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;; eval_string.lisp -- parse a string as an expression and evaluate it, or just parse it
;;
;; Copyright (C) 2005 Robert Dodier
;;
;; This program is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2 of the License, or
;; (at your option) any later version.
;;
;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;; eval_string (s) -- parse the string s as a Maxima expression and evaluate it.
;; It may or may not have a terminator (dollar sign `$' or semicolon `;').
;; Only the first expression is parsed and evaluated, if there is more than one.
;; e.g.
;; eval_string ("foo: 42; bar: foo^2 + baz") => 42
;; eval_string ("(foo: 42, bar: foo^2 + baz)") => baz + 1764
;; Complain if s is not a string.
(defun $eval_string (s)
(cond
((stringp s)
(meval (parse-string s)))
(t
(merror "eval_string: ~M is not a string." s))))
;; parse_string (s) -- parse the string s as a Maxima expression (do not evaluate it).
;; It may or may not have a terminator (dollar sign `$' or semicolon `;').
;; Only the first expression is parsed, if there is more than one.
;; e.g.
;; parse_string ("foo: 42; bar: foo^2 + baz") => foo : 42
;; parse_string ("(foo: 42, bar: foo^2 + baz)") => (foo : 42, bar : foo^2 + baz)
;; Complain if s is not a string.
(defun $parse_string (s)
(cond
((stringp s)
(parse-string s))
(t
(merror "parse_string: ~M is not a string." s))))
;; (PARSE-STRING S) -- parse the string as a Maxima expression.
;; Do not evaluate the parsed expression.
(defun parse-string (s)
(declare (special *mread-prompt*))
(with-input-from-string
(ss (ensure-terminator s))
(third (let ((*mread-prompt*)) (mread ss)))))
;; (ENSURE-TERMINATOR S) -- if the string S does not contain dollar sign `$' or semicolon `;'
;; then append a dollar sign to the end of S.
(defun ensure-terminator (s)
(cond
((or (search "$" s :test #'char-equal) (search ";" s :test #'char-equal))
s)
(t
(concatenate 'string s "$"))))
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