* lisp/calc/: Use lexical scoping in all the files

Includes the following pervasive changes:
- Move some defvars earlier in the file so they cover earlier let-bindings
- Change dynamically scoped `calc-FOO` or `math-FOO` function arguments
  to just FOO and then let-bind the `calc-FOO` or `math-FOO` variable
  explicitly in the body of the function.  In some cases, the
  beginning of the function was changed to refer to FOO so as to delay
  the binding to a nearby `let` when I could ensure that it did
  not make a difference.
- Add an underscore in front of unused vars or comment them out altogether.
- Replace unused `err` arg to `condition-case` with nil.

Plus the additional itemized changes below.

* lisp/calc/calc-map.el (calcFunc-reducer):
* lisp/calc/calc-arith.el (math-setup-declarations):
* lisp/calc/calc-help.el (calc-full-help, calc-help-index-entries)
(calc-full-help): Use `ignore-errors`.

* lisp/calc/calc-embed.el (calc-embedded-modes-change):
Declare `the-language` and `the-display-just` as dynamically scoped.

* lisp/calc/calc-forms.el (math-setup-year-holidays): Use `dolist`.

* lisp/calc/calc-graph.el (calc-graph-set-styles): Use `symbol-value`
rather than `eval.`
(calc-graph-delete-temps, calc-graph-set-styles): Use ignore-errors.

* lisp/calc/calc-macs.el (calc-with-trail-buffer): Add artificial use
of `save-buf` to silence compiler warnings in all the cases where
`body` doesn't make use of it.

* lisp/calc/calc-math.el (math-largest-emacs-expt)
(math-smallest-emacs-expt, math-use-emacs-fn): Use ignore-errors.

* lisp/calc/calc-mode.el (calc-total-algebraic-mode): Remove "P" from
interactive spec since it's not used anyway.

* lisp/calc/calc-rewr.el (calc-match): Simplify.

* lisp/calc/calc.el (calc-buffer): Give it a global nil value,
so it's automatically declared dynbound in any file that requires `calc`.
(calcDigit-nondigit): Adjust accordingly.

* lisp/calc/calcalg2.el (calcFunc-table): Declare `var-dummy` as dynbound.
(math-scan-for-limits): Comment out dead code.

* lisp/calc/calcalg3.el (math-general-fit): Declare `var-YVAL` and
`var-YVALX` as dynbound.

1 files changed, 4 insertions, 3 deletions

diff --git a/lisp/calc/calc-stuff.el b/lisp/calc/calc-stuff.el
index bbd61a2c4a8..58b81faee50 100644
--- a/lisp/calc/calc-stuff.el
+++ b/lisp/calc/calc-stuff.el
@@ -1,4 +1,4 @@
-;;; calc-stuff.el --- miscellaneous functions for Calc
+;;; calc-stuff.el --- miscellaneous functions for Calc  -*- lexical-binding:t -*-
 
 ;; Copyright (C) 1990-1993, 2001-2020 Free Software Foundation, Inc.
 
@@ -273,8 +273,9 @@ With a prefix, push that prefix as a number onto the stack."
 ;; math-map-over-constants.
 (defvar math-moc-func)
 
-(defun math-map-over-constants (math-moc-func expr)
-  (math-map-over-constants-rec expr))
+(defun math-map-over-constants (moc-func expr)
+  (let ((math-moc-func moc-func))
+    (math-map-over-constants-rec expr)))
 
 (defun math-map-over-constants-rec (expr)
   (cond ((or (Math-primp expr)