_ { return 'complex_pow(' + left + ',' + right + ')'; }
    / Factor

  Factor
    = "(" _ expr:Expression _ ")" { return expr; }
    / _ "log"  _ "(" _ arg:Expression _ ")" _ { return 'complex_log(' + arg + ')'; }
    / _ "cos"  _ "(" _ arg:Expression _ ")" _ { return 'complex_cos(' + arg + ')'; }
    / _ "sin"  _ "(" _ arg:Expression _ ")" _ { return 'complex_sin(' + arg + ')'; }
    / _ "iter" _ "(" _ arg:Expression _ "," _ count:PositiveInteger _ ")" _ {
      var n = parseInt(count) - 1, Q = arg;
     