equation 1.0.0

A Rust library for mathematical expression evaluation and simplification
Documentation 
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// An 'integer' matches one or more ASCII digits.
integer = @{ ASCII_DIGIT+ }

// The - (unary minus) operator negates the value of the operand.
unary_minus = { "-" }

// 'operation' matches any one of the four basic arithmetic operations: add, subtract, multiply, or divide.
operation = _{ add | subtract | multiply | divide | exponentiation | modulo }
    // 'add' matches the addition operator.
	add = { "+" }
    // 'subtract' matches the subtraction operator.
	subtract = { "-" }
    // 'multiply' matches the multiplication operator.
	multiply = { "*" }
    // 'divide' matches the division operator.
	divide = { "/" }
    // 'exponentiation' matches the exponential operator.
	exponentiation = { "^" | "exp" }
    // 'modulo' matches the exponential operator.
	modulo = { "%" | "mod" }

// A rule for the function names.
function_name = { "sin" | "cos" | "tan" }

// A rule for the function call.
function_call = { function_name ~ "(" ~ expression ~ ")" }

// An 'expression' consists of a 'primary' followed by zero or more 'operation-primary' pairs.
expression = { primary ~ (operation ~ primary)* }

// A 'primary' matches either an 'integer', a function call, or an expression wrapped in parentheses.
primary = _{ unary_minus? ~ ( integer | "(" ~ expression ~ ")" | function_call ) }

// An 'equation' matches the start of input, followed by an 'expression', and then the end of input.
equation = _{ SOI ~ expression ~ EOI }

// 'WHITESPACE' is used to capture and silently discard spaces.
WHITESPACE = _{ " " }