eval

func Parse ¶

func Parse(input string) (_ Expr, err error)

Parse parses the input string as an arithmetic expression.

expr = num                         a literal number, e.g., 3.14159
     | id                          a variable name, e.g., x
     | id '(' expr ',' ... ')'     a function call
     | id "++" or "--"             a postfix operator (++ or --)
     | '-' expr                    a unary operator (+-)
     | expr '+' expr               a binary operator (+-*/)