Question

I am looking for something similar to ToExpression that is available in Mathematica. I just want to convert a string to an expression, and evaluate the expression. As a first pass, my strings will include only numbers and arithmetic operators, and not even parentheses.

If I need to write it, please point me in the direction of the appropriate pre-defined modules/definitions which I should use.

Answer 1

Maybe you can use this parser for infix expressions.

http://planet.racket-lang.org/package-source/soegaard/infix.plt/1/0/planet-docs/manual/index.html

Here is a small example (it takes a while for the library to install – it seems it old Schematics test suite takes forever to install these days – I need to switch to a builtin one).

#lang at-exp racket
(require (planet soegaard/infix)
         (planet soegaard/infix/parser))
(display (format "1+2*3 is ~a\n" @${1+2*3} ))

(parse-expression #'here (open-input-string "1+2*3"))

The output will be:

1+2*3 is 7
.#<syntax:6:21 (#%infix (+ 1 (* 2 3)))>

The function parse-expression parses the expression in the string and
returns a syntax-object that resembles the output of ToExpression.