12 files changed, 921 insertions, 197 deletions

diff --git a/acprep b/acprep
index 32ca177a..b908adfc 100755
--- a/acprep
+++ b/acprep
@@ -1049,7 +1049,7 @@ class PrepareBuild(CommandLineApp):
                 line = re.sub('^\tmv -f', '\t@mv -f', line)
                 line = re.sub('^\t\$\(am__mv\)', '\t@$(am__mv)', line)
                 line = re.sub('^\t(\$\((.*?)LINK\).*)',
-                              '\t@echo "   " LD \$@;\\1 > /dev/null', line)
+                              '\t@echo "    LD " \$@;\\1 > /dev/null', line)
                 Makefile_new.write(line)
             Makefile_new.close()
             Makefile.close()
diff --git a/src/expr.cc b/src/expr.cc
index 89214d51..4f12a648 100644
--- a/src/expr.cc
+++ b/src/expr.cc
@@ -78,6 +78,16 @@ expr_t::ptr_op_t expr_t::get_op() throw()
   return ptr;
 }
 
+string expr_t::text()
+{
+  if (str.empty()) {
+    std::ostringstream out;
+    ptr->print(out);
+    set_text(out.str());
+  }
+  return str;
+}
+
 expr_t& expr_t::operator=(const expr_t& _expr)
 {
   if (this != &_expr) {
diff --git a/src/expr.h b/src/expr.h
index 24276cd1..b880fd79 100644
--- a/src/expr.h
+++ b/src/expr.h
@@ -116,10 +116,7 @@ public:
   }
 
   ptr_op_t get_op() throw();
-
-  string text() const throw() {
-    return str;
-  }
+  string   text();
 
   // This has special use in the textual parser
   void set_text(const string& txt) {
diff --git a/src/interactive.cc b/src/interactive.cc
index 1ae976e7..d2d6256b 100644
--- a/src/interactive.cc
+++ b/src/interactive.cc
@@ -62,6 +62,8 @@ void interactive_t::verify_arguments() const
   for (; ! wrong_arg && ! exit_loop && *p && next_arg; p++) {
     DEBUG("interactive.verify",
 	  "Want " << *p << " got: " << next_arg->label());
+
+    wrong_arg = false;
     switch (*p) {
     case 'a':
       label = _("an amount");
@@ -86,24 +88,24 @@ void interactive_t::verify_arguments() const
     case 'i':
     case 'l':
       label = _("an integer");
-      if (next_arg->is_long() ||
-	  (next_arg->is_amount() &&
-	   ! next_arg->as_amount().has_commodity())) {
-	wrong_arg = false;
-      }
-      else if (next_arg->is_string()) {
-	wrong_arg = false;
-	for (const char * q = next_arg->as_string().c_str(); *q; q++) {
-	  if (! std::isdigit(*q) && *q != '-') {
-	    wrong_arg = true;
-	    break;
-	  }
+    if (next_arg->is_long() ||
+	(next_arg->is_amount() &&
+	 ! next_arg->as_amount().has_commodity())) {
+      wrong_arg = false;
+    }
+    else if (next_arg->is_string()) {
+      wrong_arg = false;
+      for (const char * q = next_arg->as_string().c_str(); *q; q++) {
+	if (! std::isdigit(*q) && *q != '-') {
+	  wrong_arg = true;
+	  break;
 	}
       }
-      else {
-	wrong_arg = true;
-      }
-      break;
+    }
+    else {
+      wrong_arg = true;
+    }
+    break;
     case 'm':
       label = _("a regex");
       wrong_arg = ! next_arg->is_mask();
@@ -134,6 +136,8 @@ void interactive_t::verify_arguments() const
       dont_skip = true;
       break;
     }
+    if (wrong_arg && optional && next_arg->is_null())
+      wrong_arg = false;
 
     if (wrong_arg)
       vlabel = next_arg->label();
diff --git a/src/precmd.cc b/src/precmd.cc
index 1160cc64..590d2553 100644
--- a/src/precmd.cc
+++ b/src/precmd.cc
@@ -226,21 +226,20 @@ value_t args_command(call_scope_t& args)
   args.value().dump(out);
   out << std::endl << std::endl;
 
-  string predicate = args_to_predicate_expr(begin, end);
+  std::pair<expr_t, query_parser_t> info = args_to_predicate(begin, end);
 
   call_scope_t sub_args(static_cast<scope_t&>(args));
-  sub_args.push_back(string_value(predicate));
+  sub_args.push_back(string_value(info.first.text()));
 
   parse_command(sub_args);
 
-  if (begin != end) {
+  if (info.second.tokens_remaining()) {
     out << std::endl << _("====== Display predicate ======")
 	<< std::endl << std::endl;
 
-    predicate = args_to_predicate_expr(begin, end);
-
     call_scope_t disp_sub_args(static_cast<scope_t&>(args));
-    disp_sub_args.push_back(string_value(predicate));
+    disp_sub_args.push_back
+      (string_value(args_to_predicate(info.second).first.text()));
 
     parse_command(disp_sub_args);
   }
diff --git a/src/predicate.cc b/src/predicate.cc
index ce71a180..b3926116 100644
--- a/src/predicate.cc
+++ b/src/predicate.cc
@@ -32,175 +32,367 @@
 #include <system.hh>
 
 #include "predicate.h"
+#include "op.h"
 
 namespace ledger {
 
-string args_to_predicate_expr(value_t::sequence_t::const_iterator& begin,
-			      value_t::sequence_t::const_iterator end)
+query_lexer_t::token_t query_lexer_t::next_token()
 {
-  std::ostringstream expr;
+  if (token_cache.kind != token_t::UNKNOWN) {
+    token_t tok = token_cache;
+    token_cache = token_t();
+    return tok;
+  }
 
-  bool append_or	= false;
-  bool only_parenthesis = false;
+  if (arg_i == arg_end) {
+    if (begin == end || ++begin == end) {
+      return token_t(token_t::END_REACHED);
+    } else {
+      arg_i   = (*begin).as_string().begin();
+      arg_end = (*begin).as_string().end();
+    }
+  }
 
-  while (begin != end) {
-    string arg = (*begin).as_string();
-    string prefix;
+ resume:
+  bool consume_next = false;
+  switch (*arg_i) {
+  case ' ':
+  case '\t':
+  case '\r':
+  case '\n':
+    if (++arg_i == arg_end)
+      return next_token();
+  goto resume;
 
-    if (arg == "show") {
-      ++begin;
-      break;
+  case '/': {
+    string pat;
+    bool found_end_slash = false;
+    for (++arg_i; arg_i != arg_end; ++arg_i) {
+      if (*arg_i == '\\') {
+	if (++arg_i == arg_end)
+	  throw_(parse_error, _("Unexpected '\\' at end of pattern"));
+      }
+      else if (*arg_i == '/') {
+	++arg_i;
+	found_end_slash = true;
+	break;
+      }
+      pat.push_back(*arg_i);
     }
+    if (! found_end_slash)
+      throw_(parse_error, _("Expected '/' at end of pattern"));
+    if (pat.empty())
+      throw_(parse_error, _("Match pattern is empty"));
 
-    bool parse_argument		 = true;
-    bool only_closed_parenthesis = false;;
+    return token_t(token_t::TERM, pat);
+  }
 
-    if (arg == "not" || arg == "NOT") {
-      if (append_or)
-	prefix = " | ! ";
-      else
-	prefix = " ! ";
-      parse_argument = false;
-      append_or = false;
-    }
-    else if (arg == "and" || arg == "AND") {
-      prefix = " & ";
-      parse_argument = false;
-      append_or = false;
-    }
-    else if (arg == "or" || arg == "OR") {
-      prefix = " | ";
-      parse_argument = false;
-      append_or = false;
+  case '(': ++arg_i; return token_t(token_t::LPAREN);
+  case ')': ++arg_i; return token_t(token_t::RPAREN);
+  case '&': ++arg_i; return token_t(token_t::TOK_AND);
+  case '|': ++arg_i; return token_t(token_t::TOK_OR);
+  case '!': ++arg_i; return token_t(token_t::TOK_NOT);
+  case '@': ++arg_i; return token_t(token_t::TOK_PAYEE);
+  case '#': ++arg_i; return token_t(token_t::TOK_CODE);
+  case '%': ++arg_i; return token_t(token_t::TOK_META);
+  case '=':
+    // The '=' keyword at the beginning of a string causes the entire string
+    // to be taken as an expression.
+    if (arg_i == (*begin).as_string().begin())
+      consume_whitespace = true;
+    ++arg_i;
+    return token_t(token_t::TOK_EQ);
+
+  case '\\':
+    consume_next = true;
+    ++arg_i;
+    // fall through...
+  default: {
+    string ident;
+    string::const_iterator beg = arg_i;
+    for (; arg_i != arg_end; ++arg_i) {
+      switch (*arg_i) {
+      case ' ':
+      case '\t':
+      case '\n':
+      case '\r':
+	if (! consume_whitespace)
+	  goto test_ident;
+	else
+	  ident.push_back(*arg_i);
+	break;
+      case '(':
+      case ')':
+      case '&':
+      case '|':
+      case '!':
+      case '@':
+      case '#':
+      case '%':
+      case '=':
+	if (! consume_next)
+	  goto test_ident;
+      // fall through...
+      default:
+	ident.push_back(*arg_i);
+	break;
+      }
     }
-    else if (append_or) {
-      if (! only_parenthesis)
-	prefix = " | ";
+    consume_whitespace = false;
+
+    test_ident:
+    if (ident == "and")
+      return token_t(token_t::TOK_AND);
+    else if (ident == "or")
+      return token_t(token_t::TOK_OR);
+    else if (ident == "not")
+      return token_t(token_t::TOK_NOT);
+    else if (ident == "account")
+      return token_t(token_t::TOK_ACCOUNT);
+    else if (ident == "desc")
+      return token_t(token_t::TOK_PAYEE);
+    else if (ident == "payee")
+      return token_t(token_t::TOK_PAYEE);
+    else if (ident == "code")
+      return token_t(token_t::TOK_CODE);
+    else if (ident == "note")
+      return token_t(token_t::TOK_NOT);
+    else if (ident == "tag")
+      return token_t(token_t::TOK_META);
+    else if (ident == "meta")
+      return token_t(token_t::TOK_META);
+    else if (ident == "data")
+      return token_t(token_t::TOK_META);
+    else if (ident == "show") {
+      // The "show" keyword is special, and separates a limiting predicate
+      // from a display predicate.
+      DEBUG("pred.show", "string = " << (*begin).as_string());
+      return token_t(token_t::END_REACHED);
     }
-    else {
-      append_or = true;
+    else if (ident == "expr") {
+      // The expr keyword takes the whole of the next string as its
+      // argument.
+      consume_whitespace = true;
+      return token_t(token_t::TOK_EXPR);
     }
+    else
+      return token_t(token_t::TERM, ident);
+    break;
+  }
+  }
 
-    value_t::sequence_t::const_iterator next = begin;
-    if (++next != end) {
-      if (arg == "desc" || arg == "DESC" ||
-	  arg == "payee" || arg == "PAYEE") {
-	arg = string("@") + (*++begin).as_string();
-      }
-      else if (arg == "code" || arg == "CODE") {
-	arg = string("#") + (*++begin).as_string();
-      }
-      else if (arg == "note" || arg == "NOTE") {
-	arg = string("&") + (*++begin).as_string();
-      }
-      else if (arg == "tag" || arg == "TAG" ||
-	       arg == "meta" || arg == "META" ||
-	       arg == "data" || arg == "DATA") {
-	arg = string("%") + (*++begin).as_string();
-      }
-      else if (arg == "expr" || arg == "EXPR") {
-	arg = string("=") + (*++begin).as_string();
+  return token_t(token_t::UNKNOWN);
+}
+
+void query_lexer_t::token_t::unexpected()
+{
+  kind_t prev_kind = kind;
+
+  kind = UNKNOWN;
+
+  switch (prev_kind) {
+  case END_REACHED:
+    throw_(parse_error, _("Unexpected end of expression"));
+  case TERM:
+    throw_(parse_error, _("Unexpected string '%1'") << *value);
+  default:
+    throw_(parse_error, _("Unexpected token '%1'") << symbol());
+  }
+}
+
+void query_lexer_t::token_t::expected(char wanted, char c)
+{
+  kind = UNKNOWN;
+
+  if (c == '\0' || c == -1) {
+    if (wanted == '\0' || wanted == -1)
+      throw_(parse_error, _("Unexpected end"));
+    else
+      throw_(parse_error, _("Missing '%1'") << wanted);
+  } else {
+    if (wanted == '\0' || wanted == -1)
+      throw_(parse_error, _("Invalid char '%1'") << c);
+    else
+      throw_(parse_error, _("Invalid char '%1' (wanted '%2')") << c << wanted);
+  }
+}
+
+expr_t::ptr_op_t
+query_parser_t::parse_query_term(query_lexer_t::token_t::kind_t tok_context)
+{
+  expr_t::ptr_op_t node;
+
+  query_lexer_t::token_t tok = lexer.next_token();
+  switch (tok.kind) {
+  case query_lexer_t::token_t::END_REACHED:
+    break;
+
+  case query_lexer_t::token_t::TOK_ACCOUNT:
+  case query_lexer_t::token_t::TOK_PAYEE:
+  case query_lexer_t::token_t::TOK_CODE:
+  case query_lexer_t::token_t::TOK_NOTE:
+  case query_lexer_t::token_t::TOK_META:
+  case query_lexer_t::token_t::TOK_EXPR:
+    node = parse_query_term(tok.kind);
+    if (! node)
+      throw_(parse_error,
+	     _("%1 operator not followed by argument") << tok.symbol());
+    break;
+
+  case query_lexer_t::token_t::TERM:
+    assert(tok.value);
+    if (tok_context == query_lexer_t::token_t::TOK_META) {
+      assert(0);
+    } else {
+      node = new expr_t::op_t(expr_t::op_t::O_MATCH);
+
+      expr_t::ptr_op_t ident;
+      ident = new expr_t::op_t(expr_t::op_t::IDENT);
+      switch (tok_context) {
+      case query_lexer_t::token_t::TOK_ACCOUNT:
+	ident->set_ident("account"); break;
+      case query_lexer_t::token_t::TOK_PAYEE:
+	ident->set_ident("payee"); break;
+      case query_lexer_t::token_t::TOK_CODE:
+	ident->set_ident("code"); break;
+      case query_lexer_t::token_t::TOK_NOTE:
+	ident->set_ident("note"); break;
+      default:
+	assert(0); break;
       }
+
+      expr_t::ptr_op_t mask;
+      mask = new expr_t::op_t(expr_t::op_t::VALUE);
+      mask->set_value(mask_t(*tok.value));
+
+      node->set_left(ident);
+      node->set_right(mask);
     }
+    break;
 
-    if (parse_argument) {
-      bool in_prefix	   = true;
-      bool found_specifier = false;
-      bool no_final_slash  = false;
-
-      only_parenthesis = true;
-
-      std::ostringstream buf;
-      string parens;
-
-      for (const char * c = arg.c_str(); *c != '\0'; c++) {
-	bool consumed = false;
-
-	if (*c != '(' && *c != ')')
-	  only_parenthesis = false;
-
-	if (in_prefix) {
-	  switch (*c) {
-	  case ')':
-	    if (only_parenthesis)
-	      only_closed_parenthesis = true;
-	    // fall through...
-	  case '(':
-	    parens += c;
-	    consumed = true;
-	    break;
-	  case '@':
-	    buf << "(payee =~ /";
-	    found_specifier = true;
-	    consumed = true;
-	    break;
-	  case '#':
-	    buf << "(code =~ /";
-	    found_specifier = true;
-	    consumed = true;
-	    break;
-	  case '=':
-	    buf << "(";
-	    found_specifier = true;
-	    no_final_slash = true;
-	    consumed = true;
-	    break;
-	  case '&':
-	    buf << "(note =~ /";
-	    found_specifier = true;
-	    consumed = true;
-	    break;
-	  case '%': {
-	    bool found_metadata = false;
-	    for (const char *q = c; *q != '\0'; q++)
-	      if (*q == '=') {
-		buf << "has_tag(/"
-		     << string(c + 1, q - c - 1) << "/, /";
-		found_metadata = true;
-		c = q;
-		break;
-	      }
-	    if (! found_metadata) {
-	      buf << "has_tag(/";
-	    }
-	    found_specifier = true;
-	    consumed = true;
-	    break;
-	  }
-	  default:
-	    if (! found_specifier) {
-	      buf << parens << "(account =~ /";
-	      parens.clear();
-	      found_specifier = true;
-	    }
-	    in_prefix = false;
-	    break;
-	  }
-	}
-
-	if (! consumed)
-	  buf << *c;
-      }
+  case query_lexer_t::token_t::LPAREN:
+    node = parse_query_expr(tok_context);
+    tok = lexer.next_token();
+    if (tok.kind != query_lexer_t::token_t::RPAREN)
+      tok.expected(')');
+    break;
+
+  default:
+    lexer.push_token(tok);
+    break;
+  }
+
+  return node;
+}
+
+expr_t::ptr_op_t
+query_parser_t::parse_unary_expr(query_lexer_t::token_t::kind_t tok_context)
+{
+  expr_t::ptr_op_t node;
 
-      if (! prefix.empty() &&
-	  ! (only_parenthesis && only_closed_parenthesis))
-	expr << prefix;
+  query_lexer_t::token_t tok = lexer.next_token();
+  switch (tok.kind) {
+  case query_lexer_t::token_t::TOK_NOT: {
+    expr_t::ptr_op_t term(parse_query_term(tok_context));
+    if (! term)
+      throw_(parse_error,
+	     _("%1 operator not followed by argument") << tok.symbol());
 
-      expr << parens << buf.str();
+    node = new expr_t::op_t(expr_t::op_t::O_NOT);
+    node->set_left(term);
+    break;
+  }
 
-      if (found_specifier) {
-	if (! no_final_slash)
-	  expr << "/";
-	expr << ")";
+  default:
+    lexer.push_token(tok);
+    node = parse_query_term(tok_context);
+    break;
+  }
+
+  return node;
+}
+
+expr_t::ptr_op_t
+query_parser_t::parse_and_expr(query_lexer_t::token_t::kind_t tok_context)
+{
+  if (expr_t::ptr_op_t node = parse_unary_expr(tok_context)) {
+    while (true) {
+      query_lexer_t::token_t tok = lexer.next_token();
+      if (tok.kind == query_lexer_t::token_t::TOK_AND) {
+	expr_t::ptr_op_t prev(node);
+	node = new expr_t::op_t(expr_t::op_t::O_AND);
+	node->set_left(prev);
+	node->set_right(parse_unary_expr(tok_context));
+	if (! node->right())
+	  throw_(parse_error,
+		 _("%1 operator not followed by argument") << tok.symbol());
+      } else {
+	lexer.push_token(tok);
+	break;
       }
-    } else {
-      expr << prefix;
     }
+    return node;
+  }
+  return expr_t::ptr_op_t();
+}
 
-    begin++;
+expr_t::ptr_op_t
+query_parser_t::parse_or_expr(query_lexer_t::token_t::kind_t tok_context)
+{
+  if (expr_t::ptr_op_t node = parse_and_expr(tok_context)) {
+    while (true) {
+      query_lexer_t::token_t tok = lexer.next_token();
+      if (tok.kind == query_lexer_t::token_t::TOK_OR) {
+	expr_t::ptr_op_t prev(node);
+	node = new expr_t::op_t(expr_t::op_t::O_OR);
+	node->set_left(prev);
+	node->set_right(parse_and_expr(tok_context));
+	if (! node->right())
+	  throw_(parse_error,
+		 _("%1 operator not followed by argument") << tok.symbol());
+      } else {
+	lexer.push_token(tok);
+	break;
+      }
+    }
+    return node;
   }
+  return expr_t::ptr_op_t();
+}
 
-  return std::string("(") + expr.str() + ")";
+expr_t::ptr_op_t
+query_parser_t::parse_query_expr(query_lexer_t::token_t::kind_t tok_context)
+{
+  if (expr_t::ptr_op_t node = parse_or_expr(tok_context)) {
+    if (expr_t::ptr_op_t next = parse_query_expr(tok_context)) {
+      expr_t::ptr_op_t prev(node);
+      node = new expr_t::op_t(expr_t::op_t::O_OR);
+      node->set_left(prev);
+      node->set_right(next);
+    }
+    return node;
+  }
+  return expr_t::ptr_op_t();
+}
+
+expr_t::ptr_op_t query_parser_t::parse()
+{
+  return parse_query_expr(query_lexer_t::token_t::TOK_ACCOUNT);
+}
+
+std::pair<expr_t, query_parser_t>
+args_to_predicate(value_t::sequence_t::const_iterator begin,
+		  value_t::sequence_t::const_iterator end)
+{
+  query_parser_t parser(begin, end);
+  expr_t expr(parser.parse());
+  return std::pair<expr_t, query_parser_t>(expr, parser);
+}
+
+std::pair<expr_t, query_parser_t> args_to_predicate(query_parser_t parser)
+{
+  expr_t expr(parser.parse());
+  return std::pair<expr_t, query_parser_t>(expr, parser);
 }
 
 } // namespace ledger
diff --git a/src/predicate.h b/src/predicate.h
index 3e9fc6b1..555fac05 100644
--- a/src/predicate.h
+++ b/src/predicate.h
@@ -96,8 +96,198 @@ public:
   }
 };
 
-string args_to_predicate_expr(value_t::sequence_t::const_iterator& begin,
-			      value_t::sequence_t::const_iterator end);
+class query_lexer_t
+{
+  friend class query_parser_t;
+
+  value_t::sequence_t::const_iterator begin;
+  value_t::sequence_t::const_iterator end;
+
+  string::const_iterator arg_i;
+  string::const_iterator arg_end;
+
+  bool	  consume_whitespace;
+
+public:
+  struct token_t
+  {
+    enum kind_t {
+      UNKNOWN,
+
+      LPAREN,
+      RPAREN,
+
+      TOK_NOT,
+      TOK_AND,
+      TOK_OR,
+      TOK_EQ,
+
+      TOK_ACCOUNT,
+      TOK_PAYEE,
+      TOK_CODE,
+      TOK_NOTE,
+      TOK_META,
+      TOK_EXPR,
+
+      TERM,
+
+      END_REACHED
+
+    } kind;
+
+    optional<string> value;
+
+    explicit token_t(kind_t _kind = UNKNOWN,
+		     const optional<string>& _value = none)
+      : kind(_kind), value(_value) {
+      TRACE_CTOR(query_lexer_t::token_t, "");
+    }
+    token_t(const token_t& tok)
+      : kind(tok.kind), value(tok.value) {
+      TRACE_CTOR(query_lexer_t::token_t, "copy");
+    }
+    ~token_t() throw() {
+      TRACE_DTOR(query_lexer_t::token_t);
+    }
+
+    token_t& operator=(const token_t& tok) {
+      if (this != &tok) {
+	kind  = tok.kind;
+	value = tok.value;
+      }
+      return *this;
+    }
+
+    operator bool() const {
+      return kind != END_REACHED;
+    }
+
+    string to_string() const {
+      switch (kind) {
+      case UNKNOWN:	return "UNKNOWN";
+      case LPAREN:	return "LPAREN";
+      case RPAREN:	return "RPAREN";
+      case TOK_NOT:	return "TOK_NOT";
+      case TOK_AND:	return "TOK_AND";
+      case TOK_OR:	return "TOK_OR";
+      case TOK_EQ:	return "TOK_EQ";
+      case TOK_ACCOUNT: return "TOK_ACCOUNT";
+      case TOK_PAYEE:	return "TOK_PAYEE";
+      case TOK_CODE:	return "TOK_CODE";
+      case TOK_NOTE:	return "TOK_NOTE";
+      case TOK_META:	return "TOK_META";
+      case TOK_EXPR:	return "TOK_EXPR";
+      case TERM:	return string("TERM(") + *value + ")";
+      case END_REACHED: return "END_REACHED";
+      }
+    }
+
+    string symbol() const {
+      switch (kind) {
+      case LPAREN:	return "(";
+      case RPAREN:	return ")";
+      case TOK_NOT:	return "not";
+      case TOK_AND:	return "and";
+      case TOK_OR:	return "or";
+      case TOK_EQ:	return "=";
+      case TOK_ACCOUNT: return "account";
+      case TOK_PAYEE:	return "payee";
+      case TOK_CODE:	return "code";
+      case TOK_NOTE:	return "note";
+      case TOK_META:	return "meta";
+      case TOK_EXPR:	return "expr";
+
+      case END_REACHED: return "<EOF>";
+
+      case TERM:
+	assert(0);
+	return "<TERM>";
+
+      case UNKNOWN:
+      default:
+	assert(0);
+	return "<UNKNOWN>";
+      }
+    }
+
+    void unexpected();
+    void expected(char wanted, char c = '\0');
+  };
+
+  token_t token_cache;
+
+  query_lexer_t(value_t::sequence_t::const_iterator _begin,
+		value_t::sequence_t::const_iterator _end)
+    : begin(_begin), end(_end), consume_whitespace(false)
+  {
+    TRACE_CTOR(query_lexer_t, "");
+    assert(begin != end);
+    arg_i   = (*begin).as_string().begin();
+    arg_end = (*begin).as_string().end();
+  }
+  query_lexer_t(const query_lexer_t& lexer)
+    : begin(lexer.begin), end(lexer.end),
+      arg_i(lexer.arg_i), arg_end(lexer.arg_end),
+      consume_whitespace(lexer.consume_whitespace),
+      token_cache(lexer.token_cache)
+  {
+    TRACE_CTOR(query_lexer_t, "copy");
+  }
+  ~query_lexer_t() throw() {
+    TRACE_DTOR(query_lexer_t);
+  }
+
+  token_t next_token();
+  void    push_token(token_t tok) {
+    assert(token_cache.kind == token_t::UNKNOWN);
+    token_cache = tok;
+  }
+  token_t peek_token() {
+    if (token_cache.kind == token_t::UNKNOWN)
+      token_cache = next_token();
+    return token_cache;
+  }
+};
+
+class query_parser_t
+{
+  query_lexer_t lexer;
+
+  expr_t::ptr_op_t parse_query_term(query_lexer_t::token_t::kind_t tok_context);
+  expr_t::ptr_op_t parse_unary_expr(query_lexer_t::token_t::kind_t tok_context);
+  expr_t::ptr_op_t parse_and_expr(query_lexer_t::token_t::kind_t tok_context);
+  expr_t::ptr_op_t parse_or_expr(query_lexer_t::token_t::kind_t tok_context);
+  expr_t::ptr_op_t parse_query_expr(query_lexer_t::token_t::kind_t tok_context);
+
+public:
+  query_parser_t(value_t::sequence_t::const_iterator begin,
+		 value_t::sequence_t::const_iterator end)
+    : lexer(begin, end) {
+    TRACE_CTOR(query_parser_t, "");
+  }
+  query_parser_t(const query_parser_t& parser)
+    : lexer(parser.lexer) {
+    TRACE_CTOR(query_parser_t, "copy");
+  }
+  ~query_parser_t() throw() {
+    TRACE_DTOR(query_parser_t);
+  }
+
+  expr_t::ptr_op_t parse();
+
+  bool tokens_remaining() {
+    query_lexer_t::token_t tok = lexer.peek_token();
+    assert(tok.kind != query_lexer_t::token_t::UNKNOWN);
+    return tok.kind != query_lexer_t::token_t::END_REACHED;
+  }
+};
+
+std::pair<expr_t, query_parser_t>
+args_to_predicate(value_t::sequence_t::const_iterator begin,
+		  value_t::sequence_t::const_iterator end);
+
+std::pair<expr_t, query_parser_t>
+args_to_predicate(query_parser_t parser);
 
 } // namespace ledger
 
diff --git a/src/report.cc b/src/report.cc
index 62b54ad1..281057d3 100644
--- a/src/report.cc
+++ b/src/report.cc
@@ -380,23 +380,24 @@ namespace {
 	value_t::sequence_t::const_iterator end   =
 	  args.value().as_sequence().end();
 
-	string limit = args_to_predicate_expr(begin, end);
+	std::pair<expr_t, query_parser_t> info = args_to_predicate(begin, end);
 
+	string limit = info.first.text();
 	if (! limit.empty())
 	  report.HANDLER(limit_).on(whence, limit);
 
 	DEBUG("report.predicate",
 	      "Predicate = " << report.HANDLER(limit_).str());
 
-	string display;
-	if (begin != end)
-	  display = args_to_predicate_expr(begin, end);
+	if (info.second.tokens_remaining()) {
+	  string display = args_to_predicate(info.second).first.text();
 
-	if (! display.empty())
-	  report.HANDLER(display_).on(whence, display);
+	  if (! display.empty())
+	    report.HANDLER(display_).on(whence, display);
 
-	DEBUG("report.predicate",
-	      "Display predicate = " << report.HANDLER(display_).str());
+	  DEBUG("report.predicate",
+		"Display predicate = " << report.HANDLER(display_).str());
+	}
       }
 
       (report.*report_method)(handler_ptr(handler));
diff --git a/src/token.h b/src/token.h
index a9b75dd4..50d2bf72 100644
--- a/src/token.h
+++ b/src/token.h
@@ -108,10 +108,10 @@ struct expr_t::token_t : public noncopyable
   std::size_t length;
 
   explicit token_t() : kind(UNKNOWN), length(0) {
-    TRACE_CTOR(token_t, "");
+    TRACE_CTOR(expr_t::token_t, "");
   }
   ~token_t() throw() {
-    TRACE_DTOR(token_t);
+    TRACE_DTOR(expr_t::token_t);
   }
 
   token_t& operator=(const token_t& other) {
diff --git a/src/value.h b/src/value.h
index 9aa3cb04..31850894 100644
--- a/src/value.h
+++ b/src/value.h
@@ -818,13 +818,11 @@ public:
   }
 
   void push_back(const value_t& val) {
-    if (! val.is_null()) {
-      if (is_null())
-	*this = sequence_t();
-      if (! is_sequence())
-	in_place_cast(SEQUENCE);
-      as_sequence_lval().push_back(val);
-    }
+    if (is_null())
+      *this = sequence_t();
+    if (! is_sequence())
+      in_place_cast(SEQUENCE);
+    as_sequence_lval().push_back(val);
   }
 
   void pop_back() {
@@ -855,24 +853,18 @@ public:
   }
 
   sequence_t::iterator begin() {
-    VERIFY(is_sequence());
     return as_sequence_lval().begin();
   }
 
   sequence_t::iterator end() {
-    VERIFY(is_sequence());
-    // This special hack is because we never used end() in a context which
-    // needs us to call _dup().
-    return boost::get<sequence_t *>(storage->data)->end();
+    return as_sequence_lval().end();
   }
 
   sequence_t::const_iterator begin() const {
-    VERIFY(is_sequence());
     return as_sequence().begin();
   }
 
   sequence_t::const_iterator end() const {
-    VERIFY(is_sequence());
     return as_sequence().end();
   }
 
diff --git a/test/unit/t_expr.cc b/test/unit/t_expr.cc
index 6c88a08a..2576379e 100644
--- a/test/unit/t_expr.cc
+++ b/test/unit/t_expr.cc
@@ -3,6 +3,7 @@
 #include "t_expr.h"
 
 #include "expr.h"
+#include "predicate.h"
 
 using namespace ledger;
 
@@ -19,3 +20,309 @@ void ValueExprTestCase::tearDown()
   amount_t::shutdown();
   times_shutdown();
 }
+
+// 1.  foo and bar
+// 2.  'foo and bar'
+// 3.  (foo and bar)
+// 4.  ( foo and bar )
+// 5.  '( foo and' bar)
+// 6.  =foo and bar
+// 7.  ='foo and bar'
+// 8.  'expr foo and bar'
+// 9.  expr 'foo and bar'
+// 10. expr foo and bar
+// 11. foo and bar or baz
+// 12. foo and bar | baz
+// 13. foo and bar |baz
+// 14. foo and bar| baz
+// 15. foo and bar|baz
+// 16. foo 'and bar|baz'
+
+void ValueExprTestCase::testPredicateTokenizer1()
+{
+  value_t args;
+  args.push_back(string_value("foo"));
+  args.push_back(string_value("and"));
+  args.push_back(string_value("bar"));
+
+#ifndef NOT_FOR_PYTHON
+  query_lexer_t tokens(args.begin(), args.end());
+
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_AND,  tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::END_REACHED, tokens.next_token().kind);
+#endif
+}
+
+void ValueExprTestCase::testPredicateTokenizer2()
+{
+  value_t args;
+  args.push_back(string_value("foo and bar"));
+
+#ifndef NOT_FOR_PYTHON
+  query_lexer_t tokens(args.begin(), args.end());
+
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_AND,  tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::END_REACHED, tokens.next_token().kind);
+#endif
+}
+
+void ValueExprTestCase::testPredicateTokenizer3()
+{
+  value_t args;
+  args.push_back(string_value("(foo"));
+  args.push_back(string_value("and"));
+  args.push_back(string_value("bar)"));
+
+#ifndef NOT_FOR_PYTHON
+  query_lexer_t tokens(args.begin(), args.end());
+
+  assertEqual(query_lexer_t::token_t::LPAREN, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_AND,  tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::RPAREN, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::END_REACHED, tokens.next_token().kind);
+#endif
+}
+
+void ValueExprTestCase::testPredicateTokenizer4()
+{
+  value_t args;
+  args.push_back(string_value("("));
+  args.push_back(string_value("foo"));
+  args.push_back(string_value("and"));
+  args.push_back(string_value("bar"));
+  args.push_back(string_value(")"));
+
+#ifndef NOT_FOR_PYTHON
+  query_lexer_t tokens(args.begin(), args.end());
+
+  assertEqual(query_lexer_t::token_t::LPAREN, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_AND,  tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::RPAREN, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::END_REACHED, tokens.next_token().kind);
+#endif
+}
+
+void ValueExprTestCase::testPredicateTokenizer5()
+{
+  value_t args;
+  args.push_back(string_value("( foo and"));
+  args.push_back(string_value("bar)"));
+
+#ifndef NOT_FOR_PYTHON
+  query_lexer_t tokens(args.begin(), args.end());
+
+  assertEqual(query_lexer_t::token_t::LPAREN, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_AND,  tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::RPAREN, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::END_REACHED, tokens.next_token().kind);
+#endif
+}
+
+void ValueExprTestCase::testPredicateTokenizer6()
+{
+  value_t args;
+  args.push_back(string_value("=foo"));
+  args.push_back(string_value("and"));
+  args.push_back(string_value("bar"));
+
+#ifndef NOT_FOR_PYTHON
+  query_lexer_t tokens(args.begin(), args.end());
+
+  assertEqual(query_lexer_t::token_t::TOK_EQ, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_AND, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::END_REACHED, tokens.next_token().kind);
+#endif
+}
+
+void ValueExprTestCase::testPredicateTokenizer7()
+{
+  value_t args;
+  args.push_back(string_value("=foo and bar"));
+
+#ifndef NOT_FOR_PYTHON
+  query_lexer_t tokens(args.begin(), args.end());
+
+  assertEqual(query_lexer_t::token_t::TOK_EQ, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::END_REACHED, tokens.next_token().kind);
+#endif
+}
+
+void ValueExprTestCase::testPredicateTokenizer8()
+{
+  value_t args;
+  args.push_back(string_value("expr foo and bar"));
+
+#ifndef NOT_FOR_PYTHON
+  query_lexer_t tokens(args.begin(), args.end());
+
+  assertEqual(query_lexer_t::token_t::TOK_EXPR, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::END_REACHED, tokens.next_token().kind);
+#endif
+}
+
+void ValueExprTestCase::testPredicateTokenizer9()
+{
+  value_t args;
+  args.push_back(string_value("expr"));
+  args.push_back(string_value("foo and bar"));
+
+#ifndef NOT_FOR_PYTHON
+  query_lexer_t tokens(args.begin(), args.end());
+
+  assertEqual(query_lexer_t::token_t::TOK_EXPR, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::END_REACHED, tokens.next_token().kind);
+#endif
+}
+
+void ValueExprTestCase::testPredicateTokenizer10()
+{
+  value_t args;
+  args.push_back(string_value("expr"));
+  args.push_back(string_value("foo"));
+  args.push_back(string_value("and"));
+  args.push_back(string_value("bar"));
+
+#ifndef NOT_FOR_PYTHON
+  query_lexer_t tokens(args.begin(), args.end());
+
+  assertEqual(query_lexer_t::token_t::TOK_EXPR, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_AND,  tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::END_REACHED, tokens.next_token().kind);
+#endif
+}
+
+void ValueExprTestCase::testPredicateTokenizer11()
+{
+  value_t args;
+  args.push_back(string_value("foo"));
+  args.push_back(string_value("and"));
+  args.push_back(string_value("bar"));
+  args.push_back(string_value("or"));
+  args.push_back(string_value("baz"));
+
+#ifndef NOT_FOR_PYTHON
+  query_lexer_t tokens(args.begin(), args.end());
+
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_AND,  tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_OR,  tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::END_REACHED, tokens.next_token().kind);
+#endif
+}
+
+void ValueExprTestCase::testPredicateTokenizer12()
+{
+  value_t args;
+  args.push_back(string_value("foo"));
+  args.push_back(string_value("and"));
+  args.push_back(string_value("bar"));
+  args.push_back(string_value("|"));
+  args.push_back(string_value("baz"));
+
+#ifndef NOT_FOR_PYTHON
+  query_lexer_t tokens(args.begin(), args.end());
+
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_AND,  tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_OR,  tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::END_REACHED, tokens.next_token().kind);
+#endif
+}
+
+void ValueExprTestCase::testPredicateTokenizer13()
+{
+  value_t args;
+  args.push_back(string_value("foo"));
+  args.push_back(string_value("and"));
+  args.push_back(string_value("bar"));
+  args.push_back(string_value("|baz"));
+
+#ifndef NOT_FOR_PYTHON
+  query_lexer_t tokens(args.begin(), args.end());
+
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_AND,  tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_OR,  tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::END_REACHED, tokens.next_token().kind);
+#endif
+}
+
+void ValueExprTestCase::testPredicateTokenizer14()
+{
+  value_t args;
+  args.push_back(string_value("foo"));
+  args.push_back(string_value("and"));
+  args.push_back(string_value("bar|"));
+  args.push_back(string_value("baz"));
+
+#ifndef NOT_FOR_PYTHON
+  query_lexer_t tokens(args.begin(), args.end());
+
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_AND,  tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_OR,  tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::END_REACHED, tokens.next_token().kind);
+#endif
+}
+
+void ValueExprTestCase::testPredicateTokenizer15()
+{
+  value_t args;
+  args.push_back(string_value("foo"));
+  args.push_back(string_value("and"));
+  args.push_back(string_value("bar|baz"));
+
+#ifndef NOT_FOR_PYTHON
+  query_lexer_t tokens(args.begin(), args.end());
+
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_AND,  tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_OR,  tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::END_REACHED, tokens.next_token().kind);
+#endif
+}
+
+void ValueExprTestCase::testPredicateTokenizer16()
+{
+  value_t args;
+  args.push_back(string_value("foo"));
+  args.push_back(string_value("and bar|baz"));
+
+#ifndef NOT_FOR_PYTHON
+  query_lexer_t tokens(args.begin(), args.end());
+
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_AND,  tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TOK_OR,  tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::TERM, tokens.next_token().kind);
+  assertEqual(query_lexer_t::token_t::END_REACHED, tokens.next_token().kind);
+#endif
+}
diff --git a/test/unit/t_expr.h b/test/unit/t_expr.h
index f1289143..2f22db3d 100644
--- a/test/unit/t_expr.h
+++ b/test/unit/t_expr.h
@@ -8,6 +8,22 @@ class ValueExprTestCase : public CPPUNIT_NS::TestCase
   CPPUNIT_TEST_SUITE(ValueExprTestCase);
 
   //CPPUNIT_TEST(testConstructors);
+  CPPUNIT_TEST(testPredicateTokenizer1);
+  CPPUNIT_TEST(testPredicateTokenizer2);
+  CPPUNIT_TEST(testPredicateTokenizer3);
+  CPPUNIT_TEST(testPredicateTokenizer4);
+  CPPUNIT_TEST(testPredicateTokenizer5);
+  CPPUNIT_TEST(testPredicateTokenizer6);
+  CPPUNIT_TEST(testPredicateTokenizer7);
+  CPPUNIT_TEST(testPredicateTokenizer8);
+  CPPUNIT_TEST(testPredicateTokenizer9);
+  CPPUNIT_TEST(testPredicateTokenizer10);
+  CPPUNIT_TEST(testPredicateTokenizer11);
+  CPPUNIT_TEST(testPredicateTokenizer12);
+  CPPUNIT_TEST(testPredicateTokenizer13);
+  CPPUNIT_TEST(testPredicateTokenizer14);
+  CPPUNIT_TEST(testPredicateTokenizer15);
+  CPPUNIT_TEST(testPredicateTokenizer16);
 
   CPPUNIT_TEST_SUITE_END();
 
@@ -19,6 +35,22 @@ public:
   virtual void tearDown();
 
   //void testConstructors();
+  void testPredicateTokenizer1();
+  void testPredicateTokenizer2();
+  void testPredicateTokenizer3();
+  void testPredicateTokenizer4();
+  void testPredicateTokenizer5();
+  void testPredicateTokenizer6();
+  void testPredicateTokenizer7();
+  void testPredicateTokenizer8();
+  void testPredicateTokenizer9();
+  void testPredicateTokenizer10();
+  void testPredicateTokenizer11();
+  void testPredicateTokenizer12();
+  void testPredicateTokenizer13();
+  void testPredicateTokenizer14();
+  void testPredicateTokenizer15();
+  void testPredicateTokenizer16();
 
 private:
   ValueExprTestCase(const ValueExprTestCase &copy);