share/stringproc/eval_string.lisp

   1 ;; eval_string.lisp -- parse a string as an expression and evaluate it, or just parse it
   2 ;;
   3 ;; Copyright (C) 2005 Robert Dodier
   4 ;;
   5 ;; This program is free software; you can redistribute it and/or modify
   6 ;; it under the terms of the GNU General Public License as published by
   7 ;; the Free Software Foundation; either version 2 of the License, or
   8 ;; (at your option) any later version.
   9 ;;
  10 ;; This program is distributed in the hope that it will be useful,
  11 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 ;; GNU General Public License for more details.
  14
  15 ;; eval_string (s)  --  parse the string s as a Maxima expression and evaluate it.
  16 ;; It may or may not have a terminator (dollar sign `$' or semicolon `;').
  17 ;; Only the first expression is parsed and evaluated, if there is more than one.
  18 ;; e.g.
  19 ;; eval_string ("foo: 42; bar: foo^2 + baz")  =>  42
  20 ;; eval_string ("(foo: 42, bar: foo^2 + baz)")  =>  baz + 1764
  21 ;; Complain if s is not a string.
  22
  23 (in-package :maxima)
  24
  25 (defun $eval_string (s)
  26   (cond
  27     ((stringp s)
  28      (meval (parse-string s)))
  29     (t
  30       (merror "eval_string: ~M is not a string." s))))
  31
  32 ;; parse_string (s)  --  parse the string s as a Maxima expression (do not evaluate it).
  33 ;; It may or may not have a terminator (dollar sign `$' or semicolon `;').
  34 ;; Only the first expression is parsed, if there is more than one.
  35 ;; e.g.
  36 ;; parse_string ("foo: 42; bar: foo^2 + baz")  =>  foo : 42
  37 ;; parse_string ("(foo: 42, bar: foo^2 + baz)")  =>  (foo : 42, bar : foo^2 + baz)
  38 ;; Complain if s is not a string.
  39
  40 (defun $parse_string (s)
  41   (cond
  42     ((stringp s)
  43      (parse-string s))
  44     (t
  45       (merror "parse_string: ~M is not a string." s))))
  46
  47 ;; (PARSE-STRING S)  --  parse the string as a Maxima expression.
  48 ;; Do not evaluate the parsed expression.
  49
  50 (defun parse-string (s)
  51   (declare (special *mread-prompt* *parse-string-input-stream*))
  52   (setq *parse-string-input-stream*
  53     (make-string-input-stream (ensure-terminator s)))
  54   (let ((*mread-prompt* ""))
  55     (third (mread *parse-string-input-stream*)) ))
  56
  57 ;; (ENSURE-TERMINATOR S)  --  always concatenate a dollar sign `$' to the end of S.
  58 ;; Always concatenating a terminator is not a problem for PARSE-STRING since it only
  59 ;; parses the first expression in a string.
  60
  61 (defun ensure-terminator (s)
  62   (concatenate 'string s "$"))