tryParse method

num tryParse (String input)

Parses a string containing a number literal into a number.

Like parse except that this function returns null for invalid inputs instead of throwing.

Implementation 

static num tryParse(String input) {
  String source = input.trim();
  // TODO(lrn): Optimize to detect format and result type in one check.
  return int.tryParse(source) ?? double.tryParse(source);
}