path: root/sources/s7.h

#ifndef S7_H
#define S7_H

#define S7_VERSION "10.8"
#define S7_DATE "24-Apr-2024"
#define S7_MAJOR_VERSION 10
#define S7_MINOR_VERSION 8

#include <stdint.h>           /* for int64_t */

typedef int64_t s7_int;
typedef double s7_double;

#ifndef __cplusplus
#ifndef _MSC_VER
  #include <stdbool.h>
#else
#ifndef true
  #define bool	unsigned char
  #define true	1
  #define false	0
#endif
#endif
#endif

#if WITH_GMP
  /* in g++ these includes need to be outside the extern "C" business */
  #include <gmp.h>
  #include <mpfr.h>
  #include <mpc.h>
#endif

#ifdef __cplusplus
extern "C" {
#endif

typedef struct s7_scheme s7_scheme;
typedef struct s7_cell *s7_pointer;

s7_scheme *s7_init(void);
  /* s7_scheme is our interpreter
   * s7_pointer is a Scheme object of any (Scheme) type
   * s7_init creates the interpreter.
   */
void s7_free(s7_scheme *sc);

typedef s7_pointer (*s7_function)(s7_scheme *sc, s7_pointer args);   /* that is, obj = func(s7, args) -- args is a list of arguments */
typedef s7_pointer (*s7_pfunc)(s7_scheme *sc);

s7_pointer s7_f(s7_scheme *sc);                                      /* #f */
s7_pointer s7_t(s7_scheme *sc);                                      /* #t */
s7_pointer s7_nil(s7_scheme *sc);                                    /* () */
s7_pointer s7_undefined(s7_scheme *sc);                              /* #<undefined> */
s7_pointer s7_unspecified(s7_scheme *sc);                            /* #<unspecified> */
bool s7_is_unspecified(s7_scheme *sc, s7_pointer val);               /*     returns true if val is #<unspecified> */
s7_pointer s7_eof_object(s7_scheme *sc);                             /* #<eof> */
bool s7_is_null(s7_scheme *sc, s7_pointer p);                        /* null? */

  /* these are the Scheme constants; they do not change in value during a run,
   *   so they can be safely assigned to C global variables if desired.
   */

bool s7_is_valid(s7_scheme *sc, s7_pointer arg);                     /* does 'arg' look like an s7 object? */
bool s7_is_c_pointer(s7_pointer arg);                                /* (c-pointer? arg) */
bool s7_is_c_pointer_of_type(s7_pointer arg, s7_pointer type);
void *s7_c_pointer(s7_pointer p);
void *s7_c_pointer_with_type(s7_scheme *sc, s7_pointer p, s7_pointer expected_type, const char *caller, s7_int argnum);
s7_pointer s7_c_pointer_type(s7_pointer p);
s7_pointer s7_make_c_pointer(s7_scheme *sc, void *ptr);              /* these are for passing uninterpreted C pointers through Scheme */
s7_pointer s7_make_c_pointer_with_type(s7_scheme *sc, void *ptr, s7_pointer type, s7_pointer info);
s7_pointer s7_make_c_pointer_wrapper_with_type(s7_scheme *sc, void *ptr, s7_pointer type, s7_pointer info);

s7_pointer s7_eval_c_string(s7_scheme *sc, const char *str);         /* (eval-string str) */
s7_pointer s7_eval_c_string_with_environment(s7_scheme *sc, const char *str, s7_pointer e);
s7_pointer s7_object_to_string(s7_scheme *sc, s7_pointer arg, bool use_write);
                                                                     /* (object->string obj) */
char *s7_object_to_c_string(s7_scheme *sc, s7_pointer obj);          /* same as object->string but returns a C char* directly */
                                                                     /*   the returned value should be freed by the caller */

s7_pointer s7_load(s7_scheme *sc, const char *file);                 /* (load file) */
s7_pointer s7_load_with_environment(s7_scheme *sc, const char *filename, s7_pointer e);
s7_pointer s7_load_c_string(s7_scheme *sc, const char *content, s7_int bytes);
s7_pointer s7_load_c_string_with_environment(s7_scheme *sc, const char *content, s7_int bytes, s7_pointer e);
s7_pointer s7_load_path(s7_scheme *sc);                              /* *load-path* */
s7_pointer s7_add_to_load_path(s7_scheme *sc, const char *dir);      /* (set! *load-path* (cons dir *load-path*)) */
s7_pointer s7_autoload(s7_scheme *sc, s7_pointer symbol, s7_pointer file_or_function);  /* (autoload symbol file-or-function) */
void s7_autoload_set_names(s7_scheme *sc, const char **names, s7_int size);

  /* the load path is a list of directories to search if load can't find the file passed as its argument.
   *
   *   s7_load and s7_load_with_environment can load shared object files as well as scheme code.
   *   The scheme (load "somelib.so" (inlet 'init_func 'somelib_init)) is equivalent to
   *     s7_load_with_environment(s7, "somelib.so", s7_inlet(s7, s7_list(s7, 2, s7_make_symbol(s7, "init_func"), s7_make_symbol(s7, "somelib_init"))))
   *   s7_load_with_environment returns NULL if it can't load the file.
   */
void s7_quit(s7_scheme *sc);
  /* this tries to break out of the current evaluation, leaving everything else intact */

void (*s7_begin_hook(s7_scheme *sc))(s7_scheme *sc, bool *val);
void s7_set_begin_hook(s7_scheme *sc, void (*hook)(s7_scheme *sc, bool *val));
  /* call "hook" at the start of any block; use NULL to cancel.
   *   s7_begin_hook returns the current begin_hook function or NULL.
   */

s7_pointer s7_eval(s7_scheme *sc, s7_pointer code, s7_pointer e);    /* (eval code e) -- e is the optional environment */
s7_pointer s7_eval_with_location(s7_scheme *sc, s7_pointer code, s7_pointer e, const char *caller, const char *file, s7_int line);
void s7_provide(s7_scheme *sc, const char *feature);                 /* add feature (as a symbol) to the *features* list */
bool s7_is_provided(s7_scheme *sc, const char *feature);             /* (provided? feature) */
void s7_repl(s7_scheme *sc);

s7_pointer s7_error(s7_scheme *sc, s7_pointer type, s7_pointer info);
s7_pointer s7_wrong_type_arg_error(s7_scheme *sc, const char *caller, s7_int arg_n, s7_pointer arg, const char *descr);
s7_pointer s7_wrong_type_error(s7_scheme *sc, s7_pointer caller, s7_int arg_n, s7_pointer arg, s7_pointer descr);
  /* set arg_n to 0 to indicate that caller takes only one argument (so the argument number need not be reported */
s7_pointer s7_out_of_range_error(s7_scheme *sc, const char *caller, s7_int arg_n, s7_pointer arg, const char *descr);
s7_pointer s7_wrong_number_of_args_error(s7_scheme *sc, const char *caller, s7_pointer args);

  /* these are equivalent to (error ...) in Scheme
   *   the first argument to s7_error is a symbol that can be caught (via (catch tag ...))
   *   the rest of the arguments are passed to the error handler (if in catch)
   *   or printed out (in the default case).  If the first element of the list
   *   of args ("info") is a string, the default error handler treats it as
   *   a format control string, and passes it to format with the rest of the
   *   info list as the format function arguments.
   *
   *   s7_wrong_type_arg_error is equivalent to s7_error with a type of 'wrong-type-arg
   *   and similarly s7_out_of_range_error with type 'out-of-range.
   *
   * catch in Scheme is taken from Guile:
   *
   *  (catch tag thunk handler)
   *
   *  evaluates 'thunk'.  If an error occurs, and the type matches 'tag' (or if 'tag' is #t),
   *  the handler is called, passing it the arguments (including the type) passed to the
   *  error function.  If no handler is found, the default error handler is called,
   *  normally printing the error arguments to current-error-port.
   */

s7_pointer s7_stacktrace(s7_scheme *sc);
s7_pointer s7_history(s7_scheme *sc);                                /* the current (circular backwards) history buffer */
s7_pointer s7_add_to_history(s7_scheme *sc, s7_pointer entry);       /* add entry to the history buffer */
bool s7_history_enabled(s7_scheme *sc);
bool s7_set_history_enabled(s7_scheme *sc, bool enabled);

s7_pointer s7_gc_on(s7_scheme *sc, bool on);                         /* (gc on) */

s7_int s7_gc_protect(s7_scheme *sc, s7_pointer x);
void s7_gc_unprotect_at(s7_scheme *sc, s7_int loc);
s7_pointer s7_gc_protected_at(s7_scheme *sc, s7_int loc);
s7_pointer s7_gc_protect_via_stack(s7_scheme *sc, s7_pointer x);
s7_pointer s7_gc_protect_2_via_stack(s7_scheme *sc, s7_pointer x, s7_pointer y);
s7_pointer s7_gc_unprotect_via_stack(s7_scheme *sc, s7_pointer x);
s7_pointer s7_gc_protect_via_location(s7_scheme *sc, s7_pointer x, s7_int loc);
s7_pointer s7_gc_unprotect_via_location(s7_scheme *sc, s7_int loc);

  /* any s7_pointer object held in C (as a local variable for example) needs to be
   *   protected from garbage collection if there is any chance the GC may run without
   *   an existing Scheme-level reference to that object.  s7_gc_protect places the
   *   object in a vector that the GC always checks, returning the object's location
   *   in that table.  s7_gc_unprotect_at unprotects the object (removes it from the
   *   vector) using the location passed to it.  s7_gc_protected_at returns the object
   *   at the given location.
   *
   * You can turn the GC on and off via s7_gc_on.
   *
   * There is a built-in lag between the creation of a new object and its first possible GC
   *    (the lag time is set indirectly by GC_TEMPS_SIZE in s7.c), so you don't need to worry about
   *    very short term temps such as the arguments to s7_cons in:
   *
   *    s7_cons(s7, s7_make_real(s7, 3.14),
   *                s7_cons(s7, s7_make_integer(s7, 123), s7_nil(s7)));
   */

bool s7_is_eq(s7_pointer a, s7_pointer b);                                   /* (eq? a b) */
bool s7_is_eqv(s7_scheme *sc, s7_pointer a, s7_pointer b);                   /* (eqv? a b) */
bool s7_is_equal(s7_scheme *sc, s7_pointer a, s7_pointer b);                 /* (equal? a b) */
bool s7_is_equivalent(s7_scheme *sc, s7_pointer x, s7_pointer y);            /* (equivalent? x y) */

bool s7_is_boolean(s7_pointer x);                                            /* (boolean? x) */
bool s7_boolean(s7_scheme *sc, s7_pointer x);                                /* Scheme boolean -> C bool */
s7_pointer s7_make_boolean(s7_scheme *sc, bool x);                           /* C bool -> Scheme boolean */

  /* for each Scheme type (boolean, integer, string, etc), there are three
   *   functions: s7_<type>(...), s7_make_<type>(...), and s7_is_<type>(...):
   *
   *   s7_boolean(s7, obj) returns the C bool corresponding to the value of 'obj' (#f -> false)
   *   s7_make_boolean(s7, false|true) returns the s7 boolean corresponding to the C bool argument (false -> #f)
   *   s7_is_boolean(s7, obj) returns true if 'obj' has a boolean value (#f or #t).
   */


bool s7_is_pair(s7_pointer p);                                               /* (pair? p) */
s7_pointer s7_cons(s7_scheme *sc, s7_pointer a, s7_pointer b);               /* (cons a b) */

s7_pointer s7_car(s7_pointer p);                                             /* (car p) */
s7_pointer s7_cdr(s7_pointer p);                                             /* (cdr p) */

s7_pointer s7_set_car(s7_pointer p, s7_pointer q);                           /* (set-car! p q) */
s7_pointer s7_set_cdr(s7_pointer p, s7_pointer q);                           /* (set-cdr! p q) */

s7_pointer s7_cadr(s7_pointer p);                                            /* (cadr p) */
s7_pointer s7_cddr(s7_pointer p);                                            /* (cddr p) */
s7_pointer s7_cdar(s7_pointer p);                                            /* (cdar p) */
s7_pointer s7_caar(s7_pointer p);                                            /* (caar p) */

s7_pointer s7_caadr(s7_pointer p);                                           /* etc */
s7_pointer s7_caddr(s7_pointer p);
s7_pointer s7_cadar(s7_pointer p);
s7_pointer s7_caaar(s7_pointer p);
s7_pointer s7_cdadr(s7_pointer p);
s7_pointer s7_cdddr(s7_pointer p);
s7_pointer s7_cddar(s7_pointer p);
s7_pointer s7_cdaar(s7_pointer p);

s7_pointer s7_caaadr(s7_pointer p);
s7_pointer s7_caaddr(s7_pointer p);
s7_pointer s7_caadar(s7_pointer p);
s7_pointer s7_caaaar(s7_pointer p);
s7_pointer s7_cadadr(s7_pointer p);
s7_pointer s7_cadddr(s7_pointer p);
s7_pointer s7_caddar(s7_pointer p);
s7_pointer s7_cadaar(s7_pointer p);
s7_pointer s7_cdaadr(s7_pointer p);
s7_pointer s7_cdaddr(s7_pointer p);
s7_pointer s7_cdadar(s7_pointer p);
s7_pointer s7_cdaaar(s7_pointer p);
s7_pointer s7_cddadr(s7_pointer p);
s7_pointer s7_cddddr(s7_pointer p);
s7_pointer s7_cdddar(s7_pointer p);
s7_pointer s7_cddaar(s7_pointer p);

bool s7_is_list(s7_scheme *sc, s7_pointer p);                                /* (list? p) -> (or (pair? p) (null? p)) */
bool s7_is_proper_list(s7_scheme *sc, s7_pointer p);                         /* (proper-list? p) */
s7_int s7_list_length(s7_scheme *sc, s7_pointer a);                          /* (length a) */
s7_pointer s7_make_list(s7_scheme *sc, s7_int len, s7_pointer init);         /* (make-list len init) */
s7_pointer s7_list(s7_scheme *sc, s7_int num_values, ...);                   /* (list ...) */
s7_pointer s7_list_nl(s7_scheme *sc, s7_int num_values, ...);                /* (list ...) arglist should be NULL terminated (more error checks than s7_list) */
s7_pointer s7_array_to_list(s7_scheme *sc, s7_int num_values, s7_pointer *array); /* array contents -> list */
void s7_list_to_array(s7_scheme *sc, s7_pointer list, s7_pointer *array, int32_t len); /* list -> array (intended for old code) */
s7_pointer s7_reverse(s7_scheme *sc, s7_pointer a);                          /* (reverse a) */
s7_pointer s7_append(s7_scheme *sc, s7_pointer a, s7_pointer b);             /* (append a b) */
s7_pointer s7_list_ref(s7_scheme *sc, s7_pointer lst, s7_int num);           /* (list-ref lst num) */
s7_pointer s7_list_set(s7_scheme *sc, s7_pointer lst, s7_int num, s7_pointer val); /* (list-set! lst num val) */
s7_pointer s7_assoc(s7_scheme *sc, s7_pointer obj, s7_pointer lst);          /* (assoc obj lst) */
s7_pointer s7_assq(s7_scheme *sc, s7_pointer obj, s7_pointer x);             /* (assq obj lst) */
s7_pointer s7_member(s7_scheme *sc, s7_pointer obj, s7_pointer lst);         /* (member obj lst) */
s7_pointer s7_memq(s7_scheme *sc, s7_pointer obj, s7_pointer x);             /* (memq obj lst) */
bool s7_tree_memq(s7_scheme *sc, s7_pointer sym, s7_pointer tree);           /* (tree-memq sym tree) */


bool s7_is_string(s7_pointer p);                                             /* (string? p) */
const char *s7_string(s7_pointer p);                                         /* Scheme string -> C string (do not free the string) */
s7_pointer s7_make_string(s7_scheme *sc, const char *str);                   /* C string -> Scheme string (str is copied) */
s7_pointer s7_make_string_with_length(s7_scheme *sc, const char *str, s7_int len);  /* same as s7_make_string, but provides strlen */
s7_pointer s7_make_string_wrapper(s7_scheme *sc, const char *str);
s7_pointer s7_make_string_wrapper_with_length(s7_scheme *sc, const char *str, s7_int len);
s7_pointer s7_make_permanent_string(s7_scheme *sc, const char *str);         /* make a string that will never be GC'd */
s7_pointer s7_make_semipermanent_string(s7_scheme *sc, const char *str);     /* for (s7) string permanent within one s7 instance (freed upon s7_free) */
s7_int s7_string_length(s7_pointer str);                                     /* (string-length str) */


bool s7_is_character(s7_pointer p);                                          /* (character? p) */
uint8_t s7_character(s7_pointer p);                                          /* Scheme character -> unsigned C char */
s7_pointer s7_make_character(s7_scheme *sc, uint8_t c);                      /* unsigned C char -> Scheme character */


bool s7_is_number(s7_pointer p);                                             /* (number? p) */
bool s7_is_integer(s7_pointer p);                                            /* (integer? p) */
s7_int s7_integer(s7_pointer p);                                             /* Scheme integer -> C integer (s7_int) */
s7_pointer s7_make_integer(s7_scheme *sc, s7_int num);                       /* C s7_int -> Scheme integer */

bool s7_is_real(s7_pointer p);                                               /* (real? p) */
s7_double s7_real(s7_pointer p);                                             /* Scheme real -> C double */
s7_pointer s7_make_real(s7_scheme *sc, s7_double num);                       /* C double -> Scheme real */
s7_pointer s7_make_mutable_real(s7_scheme *sc, s7_double n);
s7_double s7_number_to_real(s7_scheme *sc, s7_pointer x);                    /* x can be any kind of number */
s7_double s7_number_to_real_with_caller(s7_scheme *sc, s7_pointer x, const char *caller);
s7_double s7_number_to_real_with_location(s7_scheme *sc, s7_pointer x, s7_pointer caller);
s7_int s7_number_to_integer(s7_scheme *sc, s7_pointer x);
s7_int s7_number_to_integer_with_caller(s7_scheme *sc, s7_pointer x, const char *caller);

bool s7_is_rational(s7_pointer arg);                                        /* (rational? arg) -- integer or ratio */
bool s7_is_ratio(s7_pointer arg);                                           /* true if arg is a ratio, not an integer */
s7_pointer s7_make_ratio(s7_scheme *sc, s7_int a, s7_int b);                /* returns the Scheme object a/b */
s7_pointer s7_rationalize(s7_scheme *sc, s7_double x, s7_double error);     /* (rationalize x error) */
s7_int s7_numerator(s7_pointer x);                                          /* (numerator x) */
s7_int s7_denominator(s7_pointer x);                                        /* (denominator x) */
s7_double s7_random(s7_scheme *sc, s7_pointer state);                       /* (random x) */
s7_pointer s7_random_state(s7_scheme *sc, s7_pointer seed);                 /* (random-state seed) */
s7_pointer s7_random_state_to_list(s7_scheme *sc, s7_pointer args);         /* (random-state->list r) */
void s7_set_default_random_state(s7_scheme *sc, s7_int seed, s7_int carry);
bool s7_is_random_state(s7_pointer p);                                      /* (random-state? p) */

bool s7_is_complex(s7_pointer arg);                                         /* (complex? arg) */
s7_pointer s7_make_complex(s7_scheme *sc, s7_double a, s7_double b);        /* returns the Scheme object a+bi */
s7_double s7_real_part(s7_pointer z);                                       /* (real-part z) */
s7_double s7_imag_part(s7_pointer z);                                       /* (imag-part z) */
char *s7_number_to_string(s7_scheme *sc, s7_pointer obj, s7_int radix);     /* (number->string obj radix) */

bool s7_is_vector(s7_pointer p);                                            /* (vector? p) */
s7_int s7_vector_length(s7_pointer vec);                                    /* (vector-length vec) */
s7_int s7_vector_rank(s7_pointer vect);                                     /* number of dimensions in vect */
s7_int s7_vector_dimension(s7_pointer vec, s7_int dim);
s7_pointer *s7_vector_elements(s7_pointer vec);                             /* a pointer to the array of s7_pointers */
s7_int *s7_int_vector_elements(s7_pointer vec);
uint8_t *s7_byte_vector_elements(s7_pointer vec);
s7_double *s7_float_vector_elements(s7_pointer vec);
bool s7_is_float_vector(s7_pointer p);                                      /* (float-vector? p) */
bool s7_is_int_vector(s7_pointer p);                                        /* (int-vector? p) */
bool s7_is_byte_vector(s7_pointer p);                                       /* (byte-vector? p) */

s7_pointer s7_vector_ref(s7_scheme *sc, s7_pointer vec, s7_int index);                            /* (vector-ref vec index) */
s7_pointer s7_vector_set(s7_scheme *sc, s7_pointer vec, s7_int index, s7_pointer a);              /* (vector-set! vec index a) */
s7_pointer s7_vector_ref_n(s7_scheme *sc, s7_pointer vector, s7_int indices, ...);                   /* multidimensional vector-ref */
s7_pointer s7_vector_set_n(s7_scheme *sc, s7_pointer vector, s7_pointer value, s7_int indices, ...); /* multidimensional vector-set! */
s7_int s7_vector_dimensions(s7_pointer vec, s7_int *dims, s7_int dims_size); /* vector dimensions */
s7_int s7_vector_offsets(s7_pointer vec, s7_int *offs, s7_int offs_size);

s7_int s7_int_vector_ref(s7_pointer vec, s7_int index);
s7_int s7_int_vector_set(s7_pointer vec, s7_int index, s7_int value);
uint8_t s7_byte_vector_ref(s7_pointer vec, s7_int index);
uint8_t s7_byte_vector_set(s7_pointer vec, s7_int index, uint8_t value);
s7_double s7_float_vector_ref(s7_pointer vec, s7_int index);
s7_double s7_float_vector_set(s7_pointer vec, s7_int index, s7_double value);

s7_pointer s7_make_vector(s7_scheme *sc, s7_int len);                                 /* (make-vector len) */
s7_pointer s7_make_int_vector(s7_scheme *sc, s7_int len, s7_int dims, s7_int *dim_info);
s7_pointer s7_make_byte_vector(s7_scheme *sc, s7_int len, s7_int dims, s7_int *dim_info);
s7_pointer s7_make_float_vector(s7_scheme *sc, s7_int len, s7_int dims, s7_int *dim_info);
s7_pointer s7_make_normal_vector(s7_scheme *sc, s7_int len, s7_int dims, s7_int *dim_info); /* make-vector but possibly multidimensional */
s7_pointer s7_make_float_vector_wrapper(s7_scheme *sc, s7_int len, s7_double *data, s7_int dims, s7_int *dim_info, bool free_data);
s7_pointer s7_make_and_fill_vector(s7_scheme *sc, s7_int len, s7_pointer fill);       /* (make-vector len fill) */

void s7_vector_fill(s7_scheme *sc, s7_pointer vec, s7_pointer obj);                   /* (vector-fill! vec obj) */
s7_pointer s7_vector_copy(s7_scheme *sc, s7_pointer old_vect);
s7_pointer s7_vector_to_list(s7_scheme *sc, s7_pointer vect);                         /* (vector->list vec) */
  /*
   *  (vect i) is the same as (vector-ref vect i)
   *  (set! (vect i) x) is the same as (vector-set! vect i x)
   *  (vect i j k) accesses the 3-dimensional vect
   *  (set! (vect i j k) x) sets that element (vector-ref and vector-set! can also be used)
   *  (make-vector (list 2 3 4)) returns a 3-dimensional vector with the given dimension sizes
   *  (make-vector '(2 3) 1.0) returns a 2-dim vector with all elements set to 1.0
   */

bool s7_is_hash_table(s7_pointer p);                                        /* (hash-table? p) */
s7_pointer s7_make_hash_table(s7_scheme *sc, s7_int size);                  /* (make-hash-table size) */
s7_pointer s7_hash_table_ref(s7_scheme *sc, s7_pointer table, s7_pointer key);
                                                                            /* (hash-table-ref table key) */
s7_pointer s7_hash_table_set(s7_scheme *sc, s7_pointer table, s7_pointer key, s7_pointer value);
                                                                            /* (hash-table-set! table key value) */
s7_int s7_hash_code(s7_scheme *sc, s7_pointer obj, s7_pointer eqfunc);      /* (hash-code obj [eqfunc]) */

s7_pointer s7_hook_functions(s7_scheme *sc, s7_pointer hook);                              /* (hook-functions hook) */
s7_pointer s7_hook_set_functions(s7_scheme *sc, s7_pointer hook, s7_pointer functions);    /* (set! (hook-functions hook) ...) */


bool s7_is_input_port(s7_scheme *sc, s7_pointer p);                         /* (input-port? p) */
bool s7_is_output_port(s7_scheme *sc, s7_pointer p);                        /* (output-port? p) */
const char *s7_port_filename(s7_scheme *sc, s7_pointer x);                  /* (port-filename p) */
s7_int s7_port_line_number(s7_scheme *sc, s7_pointer p);                    /* (port-line-number p) */

s7_pointer s7_current_input_port(s7_scheme *sc);                            /* (current-input-port) */
s7_pointer s7_set_current_input_port(s7_scheme *sc, s7_pointer p);          /* (set-current-input-port) */
s7_pointer s7_current_output_port(s7_scheme *sc);                           /* (current-output-port) */
s7_pointer s7_set_current_output_port(s7_scheme *sc, s7_pointer p);         /* (set-current-output-port) */
s7_pointer s7_current_error_port(s7_scheme *sc);                            /* (current-error-port) */
s7_pointer s7_set_current_error_port(s7_scheme *sc, s7_pointer port);       /* (set-current-error-port port) */
void s7_close_input_port(s7_scheme *sc, s7_pointer p);                      /* (close-input-port p) */
void s7_close_output_port(s7_scheme *sc, s7_pointer p);                     /* (close-output-port p) */
s7_pointer s7_open_input_file(s7_scheme *sc, const char *name, const char *mode);
                                                                            /* (open-input-file name mode) */
s7_pointer s7_open_output_file(s7_scheme *sc, const char *name, const char *mode);
                                                                            /* (open-output-file name mode) */
  /* mode here is an optional C style flag, "a" for "alter", etc ("r" is the input default, "w" is the output default) */
s7_pointer s7_open_input_string(s7_scheme *sc, const char *input_string);
                                                                            /* (open-input-string str) */
s7_pointer s7_open_output_string(s7_scheme *sc);                            /* (open-output-string) */
const char *s7_get_output_string(s7_scheme *sc, s7_pointer out_port);       /* (get-output-string port) -- current contents of output string */
  /*    don't free the string */
s7_pointer s7_output_string(s7_scheme *sc, s7_pointer p);                   /*    same but returns an s7 string */
bool s7_flush_output_port(s7_scheme *sc, s7_pointer p);                     /* (flush-output-port port) */

typedef enum {S7_READ, S7_READ_CHAR, S7_READ_LINE, S7_PEEK_CHAR, S7_IS_CHAR_READY, S7_NUM_READ_CHOICES} s7_read_t;
s7_pointer s7_open_output_function(s7_scheme *sc, void (*function)(s7_scheme *sc, uint8_t c, s7_pointer port));
s7_pointer s7_open_input_function(s7_scheme *sc, s7_pointer (*function)(s7_scheme *sc, s7_read_t read_choice, s7_pointer port));

s7_pointer s7_read_char(s7_scheme *sc, s7_pointer port);                    /* (read-char port) */
s7_pointer s7_peek_char(s7_scheme *sc, s7_pointer port);                    /* (peek-char port) */
s7_pointer s7_read(s7_scheme *sc, s7_pointer port);                         /* (read port) */
void s7_newline(s7_scheme *sc, s7_pointer port);                            /* (newline port) */
s7_pointer s7_write_char(s7_scheme *sc, s7_pointer c, s7_pointer port);     /* (write-char c port) */
s7_pointer s7_write(s7_scheme *sc, s7_pointer obj, s7_pointer port);        /* (write obj port) */
s7_pointer s7_display(s7_scheme *sc, s7_pointer obj, s7_pointer port);      /* (display obj port) */
const char *s7_format(s7_scheme *sc, s7_pointer args);                      /* (format ... */


bool s7_is_syntax(s7_pointer p);                                            /* (syntax? p) */
bool s7_is_symbol(s7_pointer p);                                            /* (symbol? p) */
const char *s7_symbol_name(s7_pointer p);                                   /* (symbol->string p) -- don't free the string */
s7_pointer s7_make_symbol(s7_scheme *sc, const char *name);                 /* (string->symbol name) */
s7_pointer s7_gensym(s7_scheme *sc, const char *prefix);                    /* (gensym prefix) */

bool s7_is_keyword(s7_pointer obj);                                         /* (keyword? obj) */
s7_pointer s7_make_keyword(s7_scheme *sc, const char *key);                 /* (string->keyword key) */
s7_pointer s7_keyword_to_symbol(s7_scheme *sc, s7_pointer key);             /* (keyword->symbol key) */

s7_pointer s7_rootlet(s7_scheme *sc);                                       /* (rootlet) */
s7_pointer s7_shadow_rootlet(s7_scheme *sc);
s7_pointer s7_set_shadow_rootlet(s7_scheme *sc, s7_pointer let);
s7_pointer s7_curlet(s7_scheme *sc);                                        /* (curlet) */
s7_pointer s7_set_curlet(s7_scheme *sc, s7_pointer e);                      /* returns previous curlet */
s7_pointer s7_outlet(s7_scheme *sc, s7_pointer e);                          /* (outlet e) */
s7_pointer s7_sublet(s7_scheme *sc, s7_pointer env, s7_pointer bindings);   /* (sublet e ...) */
s7_pointer s7_inlet(s7_scheme *sc, s7_pointer bindings);                    /* (inlet ...) */
s7_pointer s7_varlet(s7_scheme *sc, s7_pointer env, s7_pointer symbol, s7_pointer value); /* (varlet env symbol value) */
s7_pointer s7_let_to_list(s7_scheme *sc, s7_pointer env);                   /* (let->list env) */
bool s7_is_let(s7_pointer e);                                               /* )let? e) */
s7_pointer s7_let_ref(s7_scheme *sc, s7_pointer env, s7_pointer sym);       /* (let-ref e sym) */
s7_pointer s7_let_set(s7_scheme *sc, s7_pointer env, s7_pointer sym, s7_pointer val); /* (let-set! e sym val) */
s7_pointer s7_openlet(s7_scheme *sc, s7_pointer e);                         /* (openlet e) */
bool s7_is_openlet(s7_pointer e);                                           /* (openlet? e) */
s7_pointer s7_method(s7_scheme *sc, s7_pointer obj, s7_pointer method);

/* *s7* */
/* these renamed because "s7_let_field" seems the same as "s7_let", but here we're referring to *s7*, not any let */
s7_pointer s7_let_field_ref(s7_scheme *sc, s7_pointer sym);               /* (*s7* sym) */
s7_pointer s7_let_field_set(s7_scheme *sc, s7_pointer sym, s7_pointer new_value); /* (set! (*s7* sym) new_value) */
/* new names */
s7_pointer s7_starlet_ref(s7_scheme *sc, s7_pointer sym);                   /* (*s7* sym) */
s7_pointer s7_starlet_set(s7_scheme *sc, s7_pointer sym, s7_pointer new_value); /* (set! (*s7* sym) new_value) */

s7_pointer s7_name_to_value(s7_scheme *sc, const char *name);               /* name's value in the current environment (after turning name into a symbol) */
s7_pointer s7_symbol_table_find_name(s7_scheme *sc, const char *name);
s7_pointer s7_symbol_value(s7_scheme *sc, s7_pointer sym);
s7_pointer s7_symbol_set_value(s7_scheme *sc, s7_pointer sym, s7_pointer val);
s7_pointer s7_symbol_local_value(s7_scheme *sc, s7_pointer sym, s7_pointer local_env);
bool s7_for_each_symbol_name(s7_scheme *sc, bool (*symbol_func)(const char *symbol_name, void *data), void *data);
bool s7_for_each_symbol(s7_scheme *sc, bool (*symbol_func)(const char *symbol_name, void *data), void *data);

  /* these access the current environment and symbol table, providing
   *   a symbol's current binding (s7_name_to_value takes the symbol name as a char*,
   *   s7_symbol_value takes the symbol itself, s7_symbol_set_value changes the
   *   current binding, and s7_symbol_local_value uses the environment passed
   *   as its third argument).
   *
   * To iterate over the complete symbol table, use s7_for_each_symbol_name,
   *   and s7_for_each_symbol.  Both call 'symbol_func' on each symbol, passing it
   *   the symbol or symbol name, and the uninterpreted 'data' pointer.
   *   the current binding. The for-each loop stops if the symbol_func returns true,
   *   or at the end of the table.
   */

s7_pointer s7_dynamic_wind(s7_scheme *sc, s7_pointer init, s7_pointer body, s7_pointer finish);

bool s7_is_immutable(s7_pointer p);
s7_pointer s7_immutable(s7_pointer p);

void s7_define(s7_scheme *sc, s7_pointer env, s7_pointer symbol, s7_pointer value);
bool s7_is_defined(s7_scheme *sc, const char *name);
s7_pointer s7_define_variable(s7_scheme *sc, const char *name, s7_pointer value);
s7_pointer s7_define_variable_with_documentation(s7_scheme *sc, const char *name, s7_pointer value, const char *help);
s7_pointer s7_define_constant(s7_scheme *sc, const char *name, s7_pointer value);
s7_pointer s7_define_constant_with_documentation(s7_scheme *sc, const char *name, s7_pointer value, const char *help);
s7_pointer s7_define_constant_with_environment(s7_scheme *sc, s7_pointer envir, const char *name, s7_pointer value);
  /* These functions add a symbol and its binding to either the top-level environment
   *    or the 'env' passed as the second argument to s7_define.  Except for s7_define, they return
   *    the name as a symbol.
   *
   *    s7_define_variable(sc, "*features*", s7_nil(sc));
   *
   * in s7.c is equivalent to the top level form
   *
   *    (define *features* ())
   *
   * s7_define_variable is simply s7_define with string->symbol and the global environment.
   * s7_define_constant is s7_define but makes its "definee" immutable.
   * s7_define is equivalent to define in Scheme, except that it does not return the value.
   */

bool s7_is_function(s7_pointer p);
bool s7_is_procedure(s7_pointer x);                                         /* (procedure? x) */
bool s7_is_macro(s7_scheme *sc, s7_pointer x);                              /* (macro? x) */
s7_pointer s7_closure_body(s7_scheme *sc, s7_pointer p);
s7_pointer s7_closure_let(s7_scheme *sc, s7_pointer p);
s7_pointer s7_closure_args(s7_scheme *sc, s7_pointer p);
s7_pointer s7_funclet(s7_scheme *sc, s7_pointer p);                         /* (funclet x) */
bool s7_is_aritable(s7_scheme *sc, s7_pointer x, s7_int args);              /* (aritable? x args) */
s7_pointer s7_arity(s7_scheme *sc, s7_pointer x);                           /* (arity x) */
const char *s7_help(s7_scheme *sc, s7_pointer obj);                         /* (help obj) */
s7_pointer s7_make_continuation(s7_scheme *sc);                             /* call/cc... (see example below) */

const char *s7_documentation(s7_scheme *sc, s7_pointer p);                  /* (documentation x) if any (don't free the string) */
const char *s7_set_documentation(s7_scheme *sc, s7_pointer p, const char *new_doc);
s7_pointer s7_setter(s7_scheme *sc, s7_pointer obj);                        /* (setter obj) */
s7_pointer s7_set_setter(s7_scheme *sc, s7_pointer p, s7_pointer setter);   /* (set! (setter p) setter) */
s7_pointer s7_signature(s7_scheme *sc, s7_pointer func);                    /* (signature obj) */
s7_pointer s7_make_signature(s7_scheme *sc, s7_int len, ...);               /* procedure-signature data */
s7_pointer s7_make_circular_signature(s7_scheme *sc, s7_int cycle_point, s7_int len, ...);

/* possibly unsafe functions: */
s7_pointer s7_make_function(s7_scheme *sc, const char *name, s7_function fnc, s7_int required_args, s7_int optional_args, bool rest_arg, const char *doc);

/* safe functions: */
s7_pointer s7_make_safe_function(s7_scheme *sc, const char *name, s7_function fnc, s7_int required_args, s7_int optional_args, bool rest_arg, const char *doc);
s7_pointer s7_make_typed_function(s7_scheme *sc, const char *name, s7_function f,
				  s7_int required_args, s7_int optional_args, bool rest_arg, const char *doc, s7_pointer signature);

/* arglist or body possibly unsafe: */
s7_pointer s7_define_function(s7_scheme *sc, const char *name, s7_function fnc, s7_int required_args, s7_int optional_args, bool rest_arg, const char *doc);

/* arglist and body safe: */
s7_pointer s7_define_safe_function(s7_scheme *sc, const char *name, s7_function fnc, s7_int required_args, s7_int optional_args, bool rest_arg, const char *doc);
s7_pointer s7_define_typed_function(s7_scheme *sc, const char *name, s7_function fnc,
				    s7_int required_args, s7_int optional_args, bool rest_arg,
				    const char *doc, s7_pointer signature);

/* arglist unsafe or body unsafe: */
s7_pointer s7_define_unsafe_typed_function(s7_scheme *sc, const char *name, s7_function fnc,
					   s7_int required_args, s7_int optional_args, bool rest_arg,
					   const char *doc, s7_pointer signature);

/* arglist safe, body possibly unsafe: */
s7_pointer s7_define_semisafe_typed_function(s7_scheme *sc, const char *name, s7_function fnc,
					     s7_int required_args, s7_int optional_args, bool rest_arg,
					     const char *doc, s7_pointer signature);

s7_pointer s7_make_function_star(s7_scheme *sc, const char *name, s7_function fnc, const char *arglist, const char *doc);
s7_pointer s7_make_safe_function_star(s7_scheme *sc, const char *name, s7_function fnc, const char *arglist, const char *doc);
void s7_define_function_star(s7_scheme *sc, const char *name, s7_function fnc, const char *arglist, const char *doc);
void s7_define_safe_function_star(s7_scheme *sc, const char *name, s7_function fnc, const char *arglist, const char *doc);
void s7_define_typed_function_star(s7_scheme *sc, const char *name, s7_function fnc, const char *arglist, const char *doc, s7_pointer signature);
s7_pointer s7_define_macro(s7_scheme *sc, const char *name, s7_function fnc, s7_int required_args, s7_int optional_args, bool rest_arg, const char *doc);

  /* s7_make_function creates a Scheme function object from the s7_function 'fnc'.
   *   Its name (for s7_describe_object) is 'name', it requires 'required_args' arguments,
   *   can accept 'optional_args' other arguments, and if 'rest_arg' is true, it accepts
   *   a "rest" argument (a list of all the trailing arguments).  The function's documentation
   *   is 'doc'.  The s7_make_functions return the new function, but the s7_define_function (and macro)
   *   procedures return the name as a symbol (a desire for backwards compatibility brought about this split).
   *
   * s7_define_function is the same as s7_make_function, but it also adds 'name' (as a symbol) to the
   *   global (top-level) environment, with the function as its value (and returns the symbol, not the function).
   *   For example, the Scheme function 'car' is essentially:
   *
   *     s7_pointer g_car(s7_scheme *sc, s7_pointer args) {return(s7_car(s7_car(args)));}
   *
   *   then bound to the name "car":
   *
   *     s7_define_function(sc, "car", g_car, 1, 0, false, "(car obj)");
   *                                          ^ one required arg, no optional arg, no "rest" arg
   *
   * s7_is_function returns true if its argument is a function defined in this manner.
   * s7_apply_function applies the function (the result of s7_make_function) to the arguments.
   *
   * s7_define_macro defines a Scheme macro; its arguments are not evaluated (unlike a function),
   *   but the macro's returned value (assumed to be some sort of Scheme expression) is evaluated.
   *   s7_define_macro returns the name as a symbol.
   *
   * Use the "unsafe" definer if the function might call the evaluator itself in some way (s7_apply_function for example),
   *   or messes with s7's stack.
   */

  /* In s7, (define* (name . args) body) or (define name (lambda* args body))
   *   define a function that takes optional (keyword) named arguments.
   *   The "args" is a list that can contain either names (normal arguments),
   *   or lists of the form (name default-value), in any order.  When called,
   *   the names are bound to their default values (or #f), then the function's
   *   current arglist is scanned.  Any name that occurs as a keyword (":name")
   *   precedes that argument's new value.  Otherwise, as values occur, they
   *   are plugged into the environment based on their position in the arglist
   *   (as normal for a function).  So,
   *
   *   (define* (hi a (b 32) (c "hi")) (list a b c))
   *     (hi 1) -> '(1 32 "hi")
   *     (hi :b 2 :a 3) -> '(3 2 "hi")
   *     (hi 3 2 1) -> '(3 2 1)
   *
   *   :rest causes its argument to be bound to the rest of the arguments at that point.
   *
   * The C connection to this takes the function name, the C function to call, the argument
   *   list as written in Scheme, and the documentation string.  s7 makes sure the arguments
   *   are ordered correctly and have the specified defaults before calling the C function.
   *     s7_define_function_star(sc, "a-func", a_func, "arg1 (arg2 32)", "an example of C define*");
   *   Now (a-func :arg1 2) calls the C function a_func(2, 32). See the example program in s7.html.
   *
   * In s7 Scheme, define* can be used just for its optional arguments feature, but that is
   *   included in s7_define_function.  s7_define_function_star implements keyword arguments
   *   for C-level functions (as well as optional/rest arguments).
   */

s7_pointer s7_apply_function(s7_scheme *sc, s7_pointer fnc, s7_pointer args);
s7_pointer s7_apply_function_star(s7_scheme *sc, s7_pointer fnc, s7_pointer args);

s7_pointer s7_call(s7_scheme *sc, s7_pointer func, s7_pointer args);
s7_pointer s7_call_with_location(s7_scheme *sc, s7_pointer func, s7_pointer args, const char *caller, const char *file, s7_int line);
s7_pointer s7_call_with_catch(s7_scheme *sc, s7_pointer tag, s7_pointer body, s7_pointer error_handler);

  /* s7_call takes a Scheme function and applies it to 'args' (a list of arguments) returning the result.
   *   s7_pointer kar;
   *   kar = s7_make_function(sc, "car", g_car, 1, 0, false, "(car obj)");
   *   s7_integer(s7_call(sc, kar, s7_cons(sc, s7_cons(sc, s7_make_integer(sc, 123), s7_nil(sc)), s7_nil(sc))));
   *   returns 123.
   *
   * s7_call_with_location passes some information to the error handler.
   * s7_call makes sure some sort of catch exists if an error occurs during the call, but
   *   s7_apply_function does not -- it assumes the catch has been set up already.
   * s7_call_with_catch wraps an explicit catch around a function call ("body" above);
   *   s7_call_with_catch(sc, tag, body, err) is equivalent to (catch tag body err).
   */

bool s7_is_dilambda(s7_pointer obj);
s7_pointer s7_dilambda(s7_scheme *sc,
		       const char *name,
		       s7_pointer (*getter)(s7_scheme *sc, s7_pointer args),
		       s7_int get_req_args, s7_int get_opt_args,
		       s7_pointer (*setter)(s7_scheme *sc, s7_pointer args),
		       s7_int set_req_args, s7_int set_opt_args,
		       const char *documentation);
s7_pointer s7_typed_dilambda(s7_scheme *sc,
		       const char *name,
		       s7_pointer (*getter)(s7_scheme *sc, s7_pointer args),
		       s7_int get_req_args, s7_int get_opt_args,
		       s7_pointer (*setter)(s7_scheme *sc, s7_pointer args),
		       s7_int set_req_args, s7_int set_opt_args,
		       const char *documentation,
 		       s7_pointer get_sig, s7_pointer set_sig);
s7_pointer s7_dilambda_with_environment(s7_scheme *sc, s7_pointer envir,
					const char *name,
					s7_pointer (*getter)(s7_scheme *sc, s7_pointer args),
					s7_int get_req_args, s7_int get_opt_args,
					s7_pointer (*setter)(s7_scheme *sc, s7_pointer args),
					s7_int set_req_args, s7_int set_opt_args,
					const char *documentation);

s7_pointer s7_values(s7_scheme *sc, s7_pointer args);          /* (values ...) */
bool s7_is_multiple_value(s7_pointer obj);                     /*    is obj the results of (values ...) */

s7_pointer s7_make_iterator(s7_scheme *sc, s7_pointer e);      /* (make-iterator e) */
bool s7_is_iterator(s7_pointer obj);                           /* (iterator? obj) */
bool s7_iterator_is_at_end(s7_scheme *sc, s7_pointer obj);     /* (iterator-at-end? obj) */
s7_pointer s7_iterate(s7_scheme *sc, s7_pointer iter);         /* (iterate iter) */

s7_pointer s7_copy(s7_scheme *sc, s7_pointer args);            /* (copy ...) */
s7_pointer s7_fill(s7_scheme *sc, s7_pointer args);            /* (fill! ...) */
s7_pointer s7_type_of(s7_scheme *sc, s7_pointer arg);          /* (type-of arg) */



/* -------------------------------------------------------------------------------- */
/* c types/objects */

void s7_mark(s7_pointer p);

bool s7_is_c_object(s7_pointer p);
s7_int s7_c_object_type(s7_pointer obj);
void *s7_c_object_value(s7_pointer obj);
void *s7_c_object_value_checked(s7_pointer obj, s7_int type);
s7_pointer s7_make_c_object(s7_scheme *sc, s7_int type, void *value);
s7_pointer s7_make_c_object_with_let(s7_scheme *sc, s7_int type, void *value, s7_pointer let);
s7_pointer s7_make_c_object_without_gc(s7_scheme *sc, s7_int type, void *value);
s7_pointer s7_c_object_let(s7_pointer obj);
s7_pointer s7_c_object_set_let(s7_scheme *sc, s7_pointer obj, s7_pointer e);
/* the "let" in s7_make_c_object_with_let and s7_c_object_set_let needs to be GC protected by marking it in the c_object's mark function */

s7_int s7_make_c_type(s7_scheme *sc, const char *name);     /* create a new c_object type */

/* old style free/mark/equal */
void s7_c_type_set_free         (s7_scheme *sc, s7_int tag, void (*gc_free)(void *value));
void s7_c_type_set_mark         (s7_scheme *sc, s7_int tag, void (*mark)(void *value));
void s7_c_type_set_equal        (s7_scheme *sc, s7_int tag, bool (*equal)(void *value1, void *value2));

/* new style free/mark/equal and equivalent */
void s7_c_type_set_gc_free      (s7_scheme *sc, s7_int tag, s7_pointer (*gc_free)   (s7_scheme *sc, s7_pointer obj)); /* free c_object function, new style*/
void s7_c_type_set_gc_mark      (s7_scheme *sc, s7_int tag, s7_pointer (*mark)      (s7_scheme *sc, s7_pointer obj)); /* mark function, new style */
void s7_c_type_set_is_equal     (s7_scheme *sc, s7_int tag, s7_pointer (*is_equal)  (s7_scheme *sc, s7_pointer args));
void s7_c_type_set_is_equivalent(s7_scheme *sc, s7_int tag, s7_pointer (*is_equivalent)(s7_scheme *sc, s7_pointer args));

void s7_c_type_set_ref          (s7_scheme *sc, s7_int tag, s7_pointer (*ref)       (s7_scheme *sc, s7_pointer args));
void s7_c_type_set_set          (s7_scheme *sc, s7_int tag, s7_pointer (*set)       (s7_scheme *sc, s7_pointer args));
void s7_c_type_set_length       (s7_scheme *sc, s7_int tag, s7_pointer (*length)    (s7_scheme *sc, s7_pointer args));
void s7_c_type_set_copy         (s7_scheme *sc, s7_int tag, s7_pointer (*copy)      (s7_scheme *sc, s7_pointer args));
void s7_c_type_set_fill         (s7_scheme *sc, s7_int tag, s7_pointer (*fill)      (s7_scheme *sc, s7_pointer args));
void s7_c_type_set_reverse      (s7_scheme *sc, s7_int tag, s7_pointer (*reverse)   (s7_scheme *sc, s7_pointer args));
void s7_c_type_set_to_list      (s7_scheme *sc, s7_int tag, s7_pointer (*to_list)   (s7_scheme *sc, s7_pointer args));
void s7_c_type_set_to_string    (s7_scheme *sc, s7_int tag, s7_pointer (*to_string) (s7_scheme *sc, s7_pointer args));
void s7_c_type_set_getter       (s7_scheme *sc, s7_int tag, s7_pointer getter);
void s7_c_type_set_setter       (s7_scheme *sc, s7_int tag, s7_pointer setter);
/* For the copy function, either the first or second argument can be a c-object of the given type. */

  /* These functions create a new Scheme object type.  There is a simple example in s7.html.
   *
   * s7_make_c_type creates a new C-based type for Scheme.  It returns an s7_int "tag" used to indentify this type elsewhere.
   *   The functions associated with this type are set via s7_c_type_set*:
   *
   *   free:          the function called when an object of this type is about to be garbage collected
   *   mark:          called during the GC mark pass -- you should call s7_mark
   *                  on any embedded s7_pointer associated with the object (including its "let") to protect if from the GC.
   *   gc_mark and gc_free are new forms of mark and free, taking the c_object s7_pointer rather than its void* value
   *   equal:         compare two objects of this type; (equal? obj1 obj2) -- this is the old form
   *   is_equal:      compare objects as in equal? -- this is the new form of equal?
   *   is_equivalent: compare objects as in equivalent?
   *   ref:           a function that is called whenever an object of this type
   *                  occurs in the function position (at the car of a list; the rest of the list
   *                  is passed to the ref function as the arguments: (obj ...))
   *   set:           a function that is called whenever an object of this type occurs as
   *                  the target of a generalized set! (set! (obj ...) val)
   *   length:        the function called when the object is asked what its length is.
   *   copy:          the function called when a copy of the object is needed.
   *   fill:          the function called to fill the object with some value.
   *   reverse:       similarly...
   *   to_string:     object->string for an object of this type
   *   getter/setter: these help the optimizer handle applicable c-objects (see s7test.scm for an example)
   *
   * s7_is_c_object returns true if 'p' is a c_object
   * s7_c_object_type returns the c_object's type (the s7_int passed to s7_make_c_object)
   * s7_c_object_value returns the value bound to that c_object (the void *value of s7_make_c_object)
   * s7_make_c_object creates a new Scheme entity of the given type with the given (uninterpreted) value
   * s7_mark marks any Scheme c_object as in-use (use this in the mark function to mark
   *    any embedded s7_pointer variables).
   */

/* -------------------------------------------------------------------------------- */
/* the new clm optimizer!  this time for sure!
 *    d=double, i=integer, v=c_object, p=s7_pointer
 *    first return type, then arg types, d_vd -> returns double takes c_object and double (i.e. a standard clm generator)
 *
 * It is possible to tell s7 to call a foreign function directly, without any scheme-related
 *   overhead.  The call needs to take the form of one of the s7_*_t functions in s7.h.  For example,
 *   one way to call + is to pass it two s7_double arguments and get an s7_double back.  This is the
 *   s7_d_dd_t function (the first letter gives the return type, the rest give successive argument types).
 *   We tell s7 about it via s7_set_d_dd_function.  Whenever s7's optimizer encounters + with two arguments
 *   that it (the optimizer) knows are s7_doubles, in a context where an s7_double result is expected,
 *   s7 calls the s7_d_dd_t function directly without consing a list of arguments, and without
 *   wrapping up the result as a scheme cell.
 */

s7_pfunc s7_optimize(s7_scheme *sc, s7_pointer expr);

typedef s7_double (*s7_float_function)(s7_scheme *sc);
s7_float_function s7_float_optimize(s7_scheme *sc, s7_pointer expr);

typedef s7_double (*s7_d_t)(void);
void s7_set_d_function(s7_scheme *sc, s7_pointer f, s7_d_t df);
s7_d_t s7_d_function(s7_pointer f);

typedef s7_double (*s7_d_d_t)(s7_double x);
void s7_set_d_d_function(s7_scheme *sc, s7_pointer f, s7_d_d_t df);
s7_d_d_t s7_d_d_function(s7_pointer f);

typedef s7_double (*s7_d_dd_t)(s7_double x1, s7_double x2);
void s7_set_d_dd_function(s7_scheme *sc, s7_pointer f, s7_d_dd_t df);
s7_d_dd_t s7_d_dd_function(s7_pointer f);

typedef s7_double (*s7_d_ddd_t)(s7_double x1, s7_double x2, s7_double x3);
void s7_set_d_ddd_function(s7_scheme *sc, s7_pointer f, s7_d_ddd_t df);
s7_d_ddd_t s7_d_ddd_function(s7_pointer f);

typedef s7_double (*s7_d_dddd_t)(s7_double x1, s7_double x2, s7_double x3, s7_double x4);
void s7_set_d_dddd_function(s7_scheme *sc, s7_pointer f, s7_d_dddd_t df);
s7_d_dddd_t s7_d_dddd_function(s7_pointer f);

typedef s7_double (*s7_d_v_t)(void *v);
void s7_set_d_v_function(s7_scheme *sc, s7_pointer f, s7_d_v_t df);
s7_d_v_t s7_d_v_function(s7_pointer f);

typedef s7_double (*s7_d_vd_t)(void *v, s7_double d);
void s7_set_d_vd_function(s7_scheme *sc, s7_pointer f, s7_d_vd_t df);
s7_d_vd_t s7_d_vd_function(s7_pointer f);

typedef s7_double (*s7_d_vdd_t)(void *v, s7_double x1, s7_double x2);
void s7_set_d_vdd_function(s7_scheme *sc, s7_pointer f, s7_d_vdd_t df);
s7_d_vdd_t s7_d_vdd_function(s7_pointer f);

typedef s7_double (*s7_d_vid_t)(void *v, s7_int i, s7_double d);
void s7_set_d_vid_function(s7_scheme *sc, s7_pointer f, s7_d_vid_t df);
s7_d_vid_t s7_d_vid_function(s7_pointer f);

typedef s7_double (*s7_d_p_t)(s7_pointer p);
void s7_set_d_p_function(s7_scheme *sc, s7_pointer f, s7_d_p_t df);
s7_d_p_t s7_d_p_function(s7_pointer f);

typedef s7_double (*s7_d_pd_t)(s7_pointer v, s7_double x);
void s7_set_d_pd_function(s7_scheme *sc, s7_pointer f, s7_d_pd_t df);
s7_d_pd_t s7_d_pd_function(s7_pointer f);

typedef s7_double (*s7_d_7pi_t)(s7_scheme *sc, s7_pointer v, s7_int i);
void s7_set_d_7pi_function(s7_scheme *sc, s7_pointer f, s7_d_7pi_t df);
s7_d_7pi_t s7_d_7pi_function(s7_pointer f);

typedef s7_double (*s7_d_7pid_t)(s7_scheme *sc, s7_pointer v, s7_int i, s7_double d);
void s7_set_d_7pid_function(s7_scheme *sc, s7_pointer f, s7_d_7pid_t df);
s7_d_7pid_t s7_d_7pid_function(s7_pointer f);

typedef s7_double (*s7_d_id_t)(s7_int i, s7_double d);
void s7_set_d_id_function(s7_scheme *sc, s7_pointer f, s7_d_id_t df);
s7_d_id_t s7_d_id_function(s7_pointer f);

typedef s7_double (*s7_d_ip_t)(s7_int i, s7_pointer p);
void s7_set_d_ip_function(s7_scheme *sc, s7_pointer f, s7_d_ip_t df);
s7_d_ip_t s7_d_ip_function(s7_pointer f);

typedef s7_int (*s7_i_i_t)(s7_int x);
void s7_set_i_i_function(s7_scheme *sc, s7_pointer f, s7_i_i_t df);
s7_i_i_t s7_i_i_function(s7_pointer f);

typedef s7_int (*s7_i_7d_t)(s7_scheme *sc, s7_double x);
void s7_set_i_7d_function(s7_scheme *sc, s7_pointer f, s7_i_7d_t df);
s7_i_7d_t s7_i_7d_function(s7_pointer f);

typedef s7_int (*s7_i_ii_t)(s7_int i1, s7_int i2);
void s7_set_i_ii_function(s7_scheme *sc, s7_pointer f, s7_i_ii_t df);
s7_i_ii_t s7_i_ii_function(s7_pointer f);

typedef s7_int (*s7_i_7p_t)(s7_scheme *sc, s7_pointer p);
void s7_set_i_7p_function(s7_scheme *sc, s7_pointer f, s7_i_7p_t df);
s7_i_7p_t s7_i_7p_function(s7_pointer f);

typedef bool (*s7_b_p_t)(s7_pointer p);
void s7_set_b_p_function(s7_scheme *sc, s7_pointer f, s7_b_p_t df);
s7_b_p_t s7_b_p_function(s7_pointer f);

typedef s7_pointer (*s7_p_d_t)(s7_scheme *sc, s7_double x);
void s7_set_p_d_function(s7_scheme *sc, s7_pointer f, s7_p_d_t df);
s7_p_d_t s7_p_d_function(s7_pointer f);

typedef s7_pointer (*s7_p_p_t)(s7_scheme *sc, s7_pointer p);
void s7_set_p_p_function(s7_scheme *sc, s7_pointer f, s7_p_p_t df);
s7_p_p_t s7_p_p_function(s7_pointer f);

typedef s7_pointer (*s7_p_pp_t)(s7_scheme *sc, s7_pointer p1, s7_pointer p2);
void s7_set_p_pp_function(s7_scheme *sc, s7_pointer f, s7_p_pp_t df);
s7_p_pp_t s7_p_pp_function(s7_pointer f);

typedef s7_pointer (*s7_p_ppp_t)(s7_scheme *sc, s7_pointer p1, s7_pointer p2, s7_pointer p3);
void s7_set_p_ppp_function(s7_scheme *sc, s7_pointer f, s7_p_ppp_t df);
s7_p_ppp_t s7_p_ppp_function(s7_pointer f);

/* Here is an example of using these functions; more extensive examples are in clm2xen.c in sndlib, and in s7.c.
 * (This example comes from a HackerNews discussion):
 * plus.c:
 * --------
 * #include "s7.h"
 *
 * s7_pointer g_plusone(s7_scheme *sc, s7_pointer args) {return(s7_make_integer(sc, s7_integer(s7_car(args)) + 1));}
 * s7_int plusone(s7_int x) {return(x + 1);}
 *
 * void plusone_init(s7_scheme *sc)
 * {
 *   s7_define_safe_function(sc, "plusone", g_plusone, 1, 0, false, "");
 *   s7_set_i_i_function(sc, s7_name_to_value(sc, "plusone"), plusone);
 * }
 * --------
 * gcc -c plus.c -fPIC -O2 -lm
 * gcc plus.o -shared -o plus.so -ldl -lm -Wl,-export-dynamic
 * repl
 * <1> (load "plus.so" (inlet 'init_func 'plusone_init))
 * --------
 */

/* -------------------------------------------------------------------------------- */

/* maybe remove these? */
s7_pointer s7_slot(s7_scheme *sc, s7_pointer symbol);
s7_pointer s7_slot_value(s7_pointer slot);
s7_pointer s7_slot_set_value(s7_scheme *sc, s7_pointer slot, s7_pointer value);
s7_pointer s7_make_slot(s7_scheme *sc, s7_pointer env, s7_pointer symbol, s7_pointer value);
void s7_slot_set_real_value(s7_scheme *sc, s7_pointer slot, s7_double value);

/* -------------------------------------------------------------------------------- */

#if (!DISABLE_DEPRECATED)
typedef s7_int s7_Int;
typedef s7_double s7_Double;

#define s7_is_object          s7_is_c_object
#define s7_object_type        s7_c_object_type
#define s7_object_value       s7_c_object_value
#define s7_make_object        s7_make_c_object
#define s7_mark_object        s7_mark
#define s7_UNSPECIFIED(Sc)    s7_unspecified(Sc)
#endif


bool s7_is_bignum(s7_pointer obj);
#if WITH_GMP
  mpfr_t *s7_big_real(s7_pointer x);
  mpz_t  *s7_big_integer(s7_pointer x);
  mpq_t  *s7_big_ratio(s7_pointer x);
  mpc_t  *s7_big_complex(s7_pointer x);

  bool s7_is_big_real(s7_pointer x);
  bool s7_is_big_integer(s7_pointer x);
  bool s7_is_big_ratio(s7_pointer x);
  bool s7_is_big_complex(s7_pointer x);

  s7_pointer s7_make_big_real(s7_scheme *sc, mpfr_t *val);
  s7_pointer s7_make_big_integer(s7_scheme *sc, mpz_t *val);
  s7_pointer s7_make_big_ratio(s7_scheme *sc, mpq_t *val);
  s7_pointer s7_make_big_complex(s7_scheme *sc, mpc_t *val);
#endif


/* --------------------------------------------------------------------------------
 *
 *        s7 changes

 * 8-Jan-23:  s7_gc_protect_2_via_stack.
 * --------
 * 15-Nov:    s7_make_c_pointer_wrapper_with_type.
 * 17-Mar-23: moved s7_is_bignum declaration outside WITH_GMP.
 * --------
 * 9-Nov:     nan, nan-payload, +nan.<int>.
 * 19-Oct:    s7_let_field* synonyms: s7_starlet*.
 * 16-Sep:    s7_number_to_real_with_location. s7_wrong_type_error. s7_make_string_wrapper_with_length. s7_make_semipermanent_string.
 * 21-Apr:    s7_is_multiple_value.
 * 11-Apr:    removed s7_apply_*.
 * 22-Mar:    s7_eval_with_location.
 * 16-Mar:    s7_list_to_array for the s7_apply_* changes.
 * 8-Mar-22:  moved s7_apply_* to xen.h if DISABLE_DEPRECATED.
 * --------
 * 24-Nov:    moved s7_p_p_t and friends into s7.h.
 * 23-Sep:    s7_make_byte_vector, s7_is_byte_vector, s7_byte_vector_ref|set|elements.
 * 25-Aug:    s7_output_string (like s7_get_output_string, but returns an s7 string).
 * 19-Jul:    s7_is_random_state, s7_make_normal_vector. s7_array_to_list.
 * 12-Apr:    s7_optimize now returns an s7_pfunc, not an s7_function.
 * 7-Apr:     removed the "args" parameter from s7_float_function. added s7_make_c_object_without_gc.
 * 31-Mar:    vector-rank, vector-dimension.
 * 17-Mar:    removed deprecated nan.0 and inf.0 due to compiler stupidity.
 * 25-Jan:    s7_define_semisafe_typed_function.
 * 6-Jan-21:  s7_hash_code.
 * --------
 * 14-Oct:    s7_load_c_string and s7_load_c_string_with_environment.
 * 10-Sep:    s7_free.
 * 5-Aug:     s7_make_list.
 * 31-July:   s7_define_constant_with_environment and s7_dilambda_with_environment.
 * 29-July:   open-input|output-function. add S7_NUM_READ_CHOICES to s7_read_t enum and remove (unused) S7_READ_BYTE.
 * 20-July:   s7_c_pointer_with_type. notcurses_s7.c and nrepl.scm. *autoload-hook*.
 * 8-July:    s7_int|float_vector_ref|set. subvector parameter order changed.
 * 17-June:   removed deprecated *s7* accessors.
 * 20-May:    libarb_s7.c.
 * 12-May:    s7_is_big*.
 * 6-May:     added s7_scheme* initial arguments to s7_set_* opt_func calls (s7_set_d_d_function for example).
 * 23-Apr:    added s7_scheme* initial argument to s7_is_eqv.
 * 9-Mar:     move openlets to (*s7* 'openlets), s7-version to (*s7* 'version), deprecate nan.0 and inf.0.
 * 17-Feb:    s7_let_field_ref|set for *s7* access. *function* to replace __func__.
 *            deprecate __func__, s7_print_length, s7_float_format_precision, s7_set_gc_stats.
 * 31-Jan:    macro(*) and bacro(*) -- unnamed macros analogous to lambda(*).
 * 20-Jan:    debug.scm and (*s7* 'debug), trace-in, dynamic-unwind.
 *            remove coverlets (openlets is now a dilambda).
 * 10-Jan:    s7_c_type_set_gc_free and s7_c_type_set_gc_mark.
 * 2-Jan-20:  s7_c_type_set_is_equal and s7_c_type_set_is_equivalent.
 * --------
 * 2-Nov:     s7_repl.
 * 30-Oct:    change S7_DATE format, and start updating it to reflect s7.c.
 * 30-Jul:    define-expansion*.
 * 12-Jul:    s7_call_with_catch, s7_load now returns NULL if file not found (rather than raise an error).
 * 8-July:    most-positive-fixnum and most-negative-fixnum moved to *s7*.
 * 23-May:    added s7_scheme argument to s7_c_object_set_let.
 * 19-May:    s7_gc_stats renamed s7_set_gc_stats.
 * 7-May:     s7_gc_unprotect_via_stack and s7_gc_(un)protect_via_location.
 * 22-Mar:    s7_float_format_precision. port-position. port-file.
 * 4-Jan-19:  morally-equal? -> equivalent?
 * --------
 * 29-Dec:    s7_c_type_set_getter|setter (implicit c-object access).
 * 23-Dec:    remove hash-table, rename hash-table* to hash-table. add weak-hash-table.
 * 3-Dec:     deprecate s7_gc_unprotect (use s7_gc_unprotect_at).
 * 21-Nov:    added s7_history_enabled and s7_set_history_enabled.
 * 3-Nov:     removed the "value" argument from s7_for_each_symbol.
 * 22-Sep:    s7_list_nl.
 * 12-Sep:    byte-vectors can be multidimensional; homogenous vectors of any built-in type. typed hash-tables.
 * 29-Jul:    symbol-setter deprecated (use setter). s7_symbol_documentation (and setter) folded into s7_documentation.
 * 12-Jul:    changed s7_vector_dimensions|offsets.
 *            Added s7_scheme* arg to make_permanent_string and several of the optimizer functions.
 * 3-Jul:     changed make-shared-vector to subvector.
 * 20-May:    s7_keyword_to_symbol.
 * 6-May:     s7_mark_c_object -> s7_mark.
 * 26-Apr:    s7_c_type_set_to_list|string, s7_c_type_set_apply -> s7_c_type_set_ref, removed s7_c_type_set_set|apply_direct
 *            c_type length|set|ref are now s7_functions (args, not obj, etc).
 * 23-Mar:    s7_peek_char and s7_read_char now return s7_pointer, s7_write_char takes s7_pointer, not int32_t c
 *            s7_gc_protect and friends now return/take s7_int location, not uint32_t.
 *            removed s7_new_type_x.
 * 19-Mar:    int32_t -> s7_int in various functions.
 * 17-Mar:    deprecate s7_ulong and s7_ulong_long functions.
 * 26-Jan-18: s7_set_setter.
 * --------
 * 11-Dec:    s7_gc_protect_via_stack
 * 3-Oct:     renamed procedure-signature -> signature, procedure-documentation -> documentation, and procedure-setter -> setter.
 * 18-Sep:    s7_immutable, s7_is_immutable. define-constant follows lexical scope now.
 *            s7_symbol_access -> s7_symbol_setter, symbol-access -> symbol-setter.
 * 3-Aug:     object->c_object name changes.
 * 28-Jul:    s7_make_c_pointer_with_type and s7_c_pointer_type.
 * 24-Jul:    int64_t rather than long long int, and various related changes.
 * 18-Jul:    s7_make_object_with_let.
 * 8-July:    s7_define_typed_function_star, s7_make_function_star. s7_apply_function_star.
 * 27-June:   s7_make_string_wrapper.
 * 22-May:    lambda* keyword arg handling changed slightly.
 * 9-May:     s7_history, s7_add_to_history.
 * 20-Apr:    s7_tree_memq (for Snd), s7_type_of, many changes for new clm optimizer.
 * 10-Apr:    added s7_scheme first argument to s7_iterator_is_at_end.
 * 28-Mar:    removed the "rf", "pf" and "if" clm optimization functions.
 *            s7_optimize, s7_float_optimize, s7_procedure_signature.
 * 22-Feb:    removed the "gf" clm optimization functions.
 * 11-Feb:    #e, #i, #d removed. #i(...) is an int-vector constant, #r(...) a float-vector.
 * 2-Jan-17:  {apply_values} -> apply-values, {list} -> list-values, and {append} -> append.
 * --------
 * 23-Sep:    make-keyword -> string->keyword.
 * 9-Aug:     s7_varlet.
 * 29-Jul:    s7_define_unsafe_typed_function.
 * 30-May:    symbol takes any number of args.  make-vector no longer takes an optional fourth argument.
 * 24-May:    let-ref/set! check rootlet now if let is not an open let; setter for with-let.
 * 20-Feb:    removed last vestiges of quasiquoted vector support.
 * 3-Feb:     *cload-directory*.
 * 14-Jan:    profile.scm. Moved multiple-value-set! to stuff.scm. Setter for port-line-number.
 * 7-Jan:     s7_load_with_environment.
 *            s7_eval_c_string takes only one statement now (use begin to handle multiple statements)
 * 4-Jan-16:  remove s7_eval_form, change s7_eval to take its place.
 * --------
 * 11-Dec:    owlet error-history field if WITH_HISTORY=1
 * 6-Nov:     removed :key and :optional.
 * 16-Oct:    s7_make_random_state -> s7_random_state.
 * 16-Aug:    remove s7_define_integer_function, s7_function_set_removes_temp,
 *              add s7_define_typed_function, s7_make_signature.
 * 5-Aug:     added s7_scheme* arg to s7_openlet and s7_outlet.
 * 3-Jul:     s7_Double -> s7_double, s7_Int -> s7_int. Removed function_chooser_data.
 * 27-Jun:    s7_rf_t, s7_rp_t etc.
 * 19-Jun:    removed the ex_parser stuff, set_step_safe, s7_ex_fallback.
 * 5-May:     s7_make_iterator and friends.
 * 16-Apr:    added s7_fill, changed arg interpretation of s7_copy, s7_dynamic_wind.
 * 30-Mar:    s7_eval_c_string_with_environment (repl experiment).
 * 19-Mar:    repl.scm.
 * 28-Feb:    s7_vector_print_length -> s7_print_length, set case also.
 * 25-Feb:    s7_closure_* funcs to replace clumsy (deprecated) s7_procedure_source.
 * 29-Jan:    changed args to s7_new_type_x (added s7_scheme arg, fill! takes s7_function).
 * 14-Jan-15: make-iterator, iterator?
 * --------
 * 26-Dec:    s7_arity replaces s7_procedure_arity.  s7_define_integer_function. deprecate s7_procedure_name.
 * 5-Nov:     s7_shadow_rootlet and s7_set_shadow_rootlet.
 * 30-Aug:    s7_make_safe_function (for cload.scm).
 * 25-July:   define and friends now return the value, not the symbol.
 *            procedure_with_setter -> dilambda.
 *            environment -> let.  All the replaced names are deprecated.
 * 30-June:   s7_method.
 * 16-June:   remove unoptimize and s7_unoptimize.
 * 14-May:    s7_define_safe_function_star.  Removed s7_catch_all.
 * 22-Apr:    remove s7_apply_n_10, s7_is_valid_pointer, s7_keyword_eq_p.
 * 5-Mar-14:  s7_heap_size, s7_gc_freed (subsequently removed).
 * --------
 * 8-Nov:     s7_symbol_documentation, s7_define_constant_with_documentation.
 * 17-Oct:    bignum-precision (procedure-with-setter) is now an integer variable named *bignum-precision*.
 * 28-Aug:    s7_int|float_vector_elements (homogeneous vectors), libc.scm.
 * 16-Aug:    ~W directive in format, make-shared-vector.
 * 23-Jul:    s7_autoload_set_names, libm.scm, libdl.scm, libgdbm.scm, r7rs.scm, s7libtest.scm.
 * 21-Jul:    s7_is_valid (replaces deprecated s7_is_valid_pointer).
 * 24-Jun:    some bool-related changes for Windows Visual C++, including change to s7_begin_hook.
 * 3-June:    s7_autoload.
 * 28-May:    export s7_is_provided.  Added s7_scheme* arg to s7_procedure_environment.
 * 21-May:    equality predicate optional arg in make-hash-table.
 * 14-May:    glistener.c, glistener.h, s7_symbol_table_find_name (for glistener).
 * 2-May:     r7rs changes: flush-output-port, vector-append, read|write-string, boolean=?, symbol=?.
 *              start/end args for string-fill!, vector-fill!, string->list, vector->list, and copy.
 *              exit, emergency-exit.
 * 7-Apr:     removed s7_scheme* arg from s7_slot_value, added s7_is_local_variable.
 * 25-Mar:    char-position, string-position, environment-ref, environment-set! added to the scheme side.
 * 9-Jan-13:  s7_cos, s7_sin, other optimization changes.
 * --------
 * 24-Dec:    s7_set_object_array_info and other such changes.
 * 20-Nov:    removed s7_set_error_exiter and s7_error_and_exit which I think have never been used.
 * 22-Oct:    changed args to s7_function_class and s7_function_set_class.
 * 22-Aug:    symbol->dynamic-value.
 * 10-Aug:    exported s7_outer_environment.
 * 6-Aug:     removed WITH_OPTIMIZATION.
 * 25-July:   environment (in scheme). s7_vector_ref_n and s7_vector_set_n. s7_copy.
 *              added s7_scheme arg to s7_number_to_real|integer.
 * 16-July:   s7_function_returns_temp (an experiment).
 * 2-July:    s7_object_set_* functions.
 * 11-June:   throw.
 * 4-June.    s7_object_environment.
 * 31-May:    added s7_scheme argument to all the optimizer chooser functions.
 * 24-May:    open-environment?
 * 17-May:    arity, aritable?
 *            removed trace and untrace.
 * 14-May:    s7_list. s7_procedure_set_setter.  Removed s7_procedure_getter.
 *              procedure-setter is settable: removed most of procedure-with-setter.
 *            make-type replaced by open-environment.
 * 11-May:    s7 2.0: hook implementation changed completely.
 *            s7_environment_ref|set.
 * 4-May:     *error-info* replaced by error-environment, and stacktrace has changed.
 * 22-Apr:    #_<name> = startup (built-in) value of name
 * 17-Apr:    with-baffle.
 * 14-Apr:    WITH_SYSTEM_EXTRAS (default 0) has additional OS and IO functions:
 *              directory? file-exists? delete-file getenv directory->list system
 * 26-Mar:    "@" as exponent, WITH_AT_SIGN_AS_EXPONENT switch (default is 1).
 * 18-Mar:    removed *trace-hook*.
 * 6-Feb:     random-state?, hash-table-iterator?, and morally-equal?
 * 18-Jan:    s7_environment_to_list and environment->list return just the local environment's bindings.
 *            outer-environment returns the environment enclosing its argument (an environment).
 *            environments are now applicable objects.
 *            added the object system example to s7.html.
 * 12-Jan:    added reverse argument to s7_new_type_x.  This is needed because an object might implement
 *              the apply and set methods, but they might refer to different things.
 * 6-Jan-12:  added (scheme side) logbit?.
 * --------
 * 21-Dec:    s7_eval, s7_make_slot, s7_slot_set_value.
 *            changed s7_symbol_slot to s7_slot, and s7_symbol_slot_value to s7_slot_value.
 * 26-Oct:    s7_procedure_name.
 * 6-Oct:     changed s7_make_closure args: split the code argument in two (args and body).
 *               s7_make_closure(... code ...) is now s7_make_closure(... car(code), cdr(code) ...)
 *            s7_is_environment.
 * 19-Aug:    s7_function_chooser_data.
 * 11-Aug:    s7_symbol_accessor functions. s7_cxxxxr.
 * 9-Aug:     s7_function_chooser, s7_function_choice, s7_function_choice_set_direct.
 * 20-Jul:    s7_function_class, s7_function_set_class, and s7_function_set_chooser.
 * 14-Jul:    removed thread and profiling support.
 * 5-June:    s7_define_safe_function and s7_unoptimize exported; added unoptimize function in scheme.
 * 30-May:    environment->list and s7_environment_to_list since environments are no longer alists internally.
 * 26-May:    added s7_scheme argument to s7_procedure_setter and getter (old names had "with_setter_").
 * 28-Apr:    s7_help.
 * 5-Apr:     pair-line-number.
 * 14-Mar:    s7_make_random_state, optional state argument to s7_random, random-state->list, s7_random_state_to_list.
 * 10-Feb:    s7_vector_print_length, s7_set_vector_print_length.
 * 7-Feb:     s7_begin_hook, s7_set_begin_hook.
 * 25-Jan:    s7_is_thread, s7_thread, s7_make_thread, s7_thread_s7, s7_thread_data.
 *               s7_is_lock, s7_make_lock, s7_lock.
 *               changed s7_thread_variable_value to s7_thread_variable.
 * 23-Jan:    removed (scheme-level) quit.
 * 17-Jan-11: make-hash-table-iterator.
 *            map and for-each accept any applicable object as the first argument.
 *            format's ~{...~} directive can handle any applicable object.
 * --------
 * 17-Dec:    removed unquote-splicing; replaced by (unquote (apply values ...)).
 * 12-Dec:    environment?
 * 7-Dec:     member and assoc have an optional third arg, the comparison function.
 * 1-Dec:     *gc-stats* in Scheme, s7_gc_stats in C.
 *            gmp and gtk-repl examples in s7.html.
 * 21-Nov:    Load C module example in s7.html.
 * 12-Nov:    *trace-hook*, *load-hook*, *error-hook*, and *unbound-variable-hook* are now s7 hooks.
 * 9-Nov:     hooks: C side: s7_is_hook, s7_make_hook, s7_hook_apply, s7_hook_functions, s7_hook_arity, s7_hook_documentation.
 *                   s7 side: hook?, make-hook, hook, hook-apply, hook-functions, hook-arity, hook-documentation.
 * 8-Nov:     Closure defined in C example in s7.html.
 * 23-Oct:    s7_call_with_location for better error reporting.
 * 19-Oct:    *stdin*, *stdout*, *stderr* for default IO ports (rather than nil which is ambiguous).
 * 14-Oct:    removed special variable support.
 * 30-Sep:    setters for current-input-port, current-output-port, and current-error-port.
 * 30-Aug:    :allow-other-keys in define*.
 * 10-Aug:    added boolean argument use_write to s7_object_to_string (true=write, false=display).
 * 30-July:   special macro for access to dynamic binding.
 *            s7_symbol_special_value for C-side access to dynamic bindings.
 *            s7_is_macro.
 *            port-closed? returns #t if its argument (a port) is closed.
 * 22-July:   s7_make_character takes uint32_t, rather than int.
 *            added symbol function for funny symbol names.
 * 12-July:   initial-environment.
 * 7-July:    removed force and delay: use slib.
 * 3-July:    new backquote implementation.
 * 28-June:   syntactic keywords (e.g. lambda) are applicable.
 * 7-June:    changed key arg in s7_hash_table_ref|set to be s7_pointer, not const char*.
 *            hash-tables can now handle any s7 object as the key.
 *            map and for-each now pass a hash-table entry to the function, rather than an internal alist.
 *            reverse of a hash-table reverses the keys and values (i.e. old value becomes new key, etc).
 * 2-June:    removed procedure-with-setter-setter-arity and folded that info into procedure-arity (use cdddr).
 * 22-May:    multidimensional vectors are no longer optional.
 * 9-May:     s7_read_char and s7_peek_char have to return an int, not a char (<eof>=-1, but 255 is a legit char).
 *            s7_write_char and s7_open_output_function have similar changes.
 * 3-May:     *#readers* to customize #... reading.  Also nan? and infinite?.
 *            multidimensional vector constants using #nD(...): (#2D((1 2 3) (4 5 6)) 0 0) -> 1.
 * 13-Apr:    removed hash-table|vector|string-for-each -- these are handled by for-each.
 *            also removed vector-map -- map is generic, but always returns a list.
 * 12-Apr:    removed immutable constant checks -- see s7.html.
 * 7-Apr:     *unbound-variable-hook*.
 *            augment-environment and s7_augment_environment.
 * 29-Mar:    symbol-access, s7_symbol_access, s7_symbol_set_access.
 *            C example of notification in s7.html.
 * 25-Mar:    make-type.  s7_is_equal now includes an s7_scheme pointer as its first argument.
 * 24-Mar:    s7_is_defined.
 * 19-Mar:    removed encapsulation mechanism and s7_define_set_function.
 * 18-Mar:    added macro?.
 * 27-Feb:    removed r4rs-style macro syntax.
 * 17-Feb:    s7_number_to_integer.
 * 20-Jan-10: removed the stack function.
 * --------
 * 16-Dec:    hash-table-for-each.
 * 1-Dec:     mpc versions before 0.8.0 are no longer supported.
 * 24-Nov:    define-macro* and defmacro*.
 *            force and delay included only if WITH_FORCE set, promise? removed.
 * 17-Nov:    s7_is_boolean no longer takes the s7_scheme argument.
 * 7-Nov:     s7_vector_dimensions, s7_vector_offsets, example of use.
 * 3-Nov:     s7_vector_rank.
 * 30-Oct:    *trace-hook*.
 * 12-Oct:    s7_port_filename.
 * 5-Oct:     s7_c_pointer and friends.
 * 14-Sep:    s7_values, s7_make_continuation, and a better interrupt example.
 *            vector-for-each, vector-map, string-for-each.
 * 7-Sep:     s7_open_input_function. with-environment. receive.
 * 3-Sep:     s7.html, s7-slib-init.scm.
 *            s7_stacktrace in s7.h.
 * 27-Aug:    vector and hash-table sizes are now s7_ints, rather than ints.
 * 20-Aug:    s7_remove_from_heap.
 * 17-Aug:    *error-info*.
 * 7-Aug:     s7_define_function_with_setter.
 *            s7_quit and example of signal handling.
 * 6-Aug:     encapsulation.  s7_define_set_function.  s7_new_type_x.
 *            generic function: copy, and length is generic.
 * 1-Aug:     lower-case versions of s7_T and friends.
 *            s7_define_macro. macroexpand.
 *            strings are set-applicable (like vectors).
 * 31-Jul:    *error-hook*.
 * 30-Jul:    changed backtrace handling: removed backtrace stuff, added stacktrace.
 *            removed gc-verbose and load-verbose replaced by *load-hook*.
 * 23-Jul:    __func__.
 * 20-Jul:    trace and untrace.
 * 14-Jul:    replaced s7_make_closure_star with s7_define_function_star.
 * 29-Jun:    s7_format declaration.
 * 12-May:    s7_is_constant.
 * 20-Apr:    changed rationalize to be both r5rs-acceptable and fast.
 * 6-Apr:     added s7_make_permanent_string.
 * 14-Mar:    removed s7_local_gc_protect and s7_local_gc_unprotect.
 * 4-Mar:     multidimensional and applicable vectors.
 * 1-Mar:     s7_random added to s7.h.
 * 29-Jan:    s7_is_bignum and friends.
 * 26-Jan:    added s7_scheme arg to s7_vector_fill.
 * 16-Jan:    s7_is_ulong_long and friends for C pointers in 64-bit situations.
 * 9-Jan-09   multiprecision arithmetic (gmp, mpfr, mpc) on the WITH_GMP switch
 * --------
 * 29-Dec:    "+" specialization example, s7_apply_function.
 * 3-Dec:     s7_open_output_function.
 * 30-Nov:    s7_wrong_number_of_args_error.
 * 24-Nov:    changed s7_make_counted_string to s7_make_string_with_length.
 *              also added built-in format and define*
 * 10-Nov:    s7_define_constant,
 *              built-in (scheme-side) pi, most-positive-fixnum, most-negative-fixnum
 * 7-Nov:     removed s7_is_immutable and friends, s7_reverse_in_place.
 *              removed the s7_pointer arg to s7_gc_on.
 *              added s7_UNSPECIFIED
 * 25-Oct:    added name arg to s7_make_procedure_with_setter,
 *              and s7_scheme arg to new_type print func.
 * 1-Oct-08   version 1.0
 */


#ifdef __cplusplus
}
#endif

#endif