MCGExpression

This is a PHP expression parser and comparison tool, written to grade MathCounts answers for http://github.com/saligrama/mathcountsgrading

Setup

Clone the repository.

$ git clone http://github.com/saligrama/MCGExpression

Usage

In MCGExpression/main.php, you'll find these contents.

#!/usr/bin/env php
<?php

    require("new_slice.php");
    require("unary_minus.php");
    require("tokenizer.php");
    require("shunting_yard.php");
    require("compare.php");

    // always run this function first before doing anything else
    // relied upon by tokenizer and shunting_yard
    declare_globals();

?>

In this state, the system does nothing. You can add something like this to the end.

$expr1 = "-3-7SQRT(8PI-1)";
$expr2 = "-7SQRT(-1+8PI)-3";

$e1_tok = tokenize($expr1);
$e2_tok = tokenize($expr2);

echo compare(
    shunting_yard($e1_tok[0], $e1_tok[1]),
    shunting_yard($e2_tok[0], $e2_tok[1])
);

Run the program:

$ ./main.php

The result from the code above:

1

You can change the values for $expr1 and $expr2 and play around with the system.

Constants and functions can be entered as below:

Constant/function	Enter as
π	PI
√	SQRT
e	E
i	I
sin, cos, tan, and other functions	Uppercased text representation

For more details, please view the declare_globals() function in MCGExpression/tokenizer.php.