calc.phpeg

calc
  = expression !.


// left associative
expression
  = f:factor ( "+" g:factor { $f = $f + $g; }
             / "-" g:factor { $f = $f - $g; }
             )*
    -> $f

factor
  = t:term ( "*" u:term { $t = $t * $u; }
           / "/" u:term { $t = $t / $u; }
           )*
    -> $t


// right associative
term
  = p:primary "^" t:term -> pow($p, $t)
  / primary


// primary
primary
  = __ "pi" __
    -> M_PI

  / __ "e" __
    -> 2.718281828459

  / __ f:function? __ '(' e:expression ')' __
    {
        if ($f) {
            return $f($e);
        }

        return $e;
    }

  / __ n:[0-9]+ __
    -> intval($n)

function
  = "abs"
  / "sin"
  / "asin"
  / "cos"
  / "acos"
  / "tan"
  / "atan"
  / "exp"
  / "ln" -> "log"
  / "log10"
  / "sqrt"

__
  = [ \t\r\n]*