Clone this repo:
  1. 17b2bc8 Revert "Revert "Remove dependency on package:charcode (#29)" (#33)" (#36) by Nate Bosch · 4 weeks ago master
  2. 0e53bf9 Prepare for stable release of null safety (#34) by Nate Bosch · 5 weeks ago 1.1.0
  3. 1719b93 Revert "Remove dependency on package:charcode (#29)" (#33) by Nate Bosch · 5 weeks ago
  4. 8bd12d5 Migrate to GitHub Actions (#32) by Alexander Thomas · 6 weeks ago
  5. 7e41395 Remove dependency on package:charcode (#29) by Nate Bosch · 4 months ago

This package exposes a StringScanner type that makes it easy to parse a string using a series of Patterns. For example:

import 'dart:math' as math;

import 'package:string_scanner/string_scanner.dart';

num parseNumber(String source) {
  // Scan a number ("1", "1.5", "-3").
  final scanner = StringScanner(source);

  // [Scanner.scan] tries to consume a [Pattern] and returns whether or not it
  // succeeded. It will move the scan pointer past the end of the pattern.
  final negative = scanner.scan('-');

  // [Scanner.expect] consumes a [Pattern] and throws a [FormatError] if it
  // fails. Like [Scanner.scan], it will move the scan pointer forward.
  scanner.expect(RegExp(r'\d+'));

  // [Scanner.lastMatch] holds the [MatchData] for the most recent call to
  // [Scanner.scan], [Scanner.expect], or [Scanner.matches].
  var number = num.parse(scanner.lastMatch[0]);

  if (scanner.scan('.')) {
    scanner.expect(RegExp(r'\d+'));
    final decimal = scanner.lastMatch[0];
    number += int.parse(decimal) / math.pow(10, decimal.length);
  }

  // [Scanner.expectDone] will throw a [FormatError] if there's any input that
  // hasn't yet been consumed.
  scanner.expectDone();

  return (negative ? -1 : 1) * number;
}