https://github.com/dart-lang/string_scanner

A class for parsing strings using a sequence of patterns.
https://github.com/dart-lang/string_scanner

Last synced: 4 months ago
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A class for parsing strings using a sequence of patterns.

• Host: GitHub
• URL: https://github.com/dart-lang/string_scanner
• Owner: dart-lang
• License: bsd-3-clause
• Created: 2014-12-18T00:54:42.000Z (over 10 years ago)
• Default Branch: master
• Last Pushed: 2024-12-17T09:59:00.000Z (6 months ago)
• Last Synced: 2025-02-05T20:18:48.732Z (4 months ago)
• Language: Dart
• Homepage: https://pub.dev/packages/string_scanner
• Size: 161 KB
• Stars: 59
• Watchers: 37
• Forks: 18
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE

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README

        
> [!IMPORTANT]  

> This repo has moved to https://github.com/dart-lang/tools/tree/main/pkgs/string_scanner

[![Dart CI](https://github.com/dart-lang/string_scanner/actions/workflows/test-package.yml/badge.svg)](https://github.com/dart-lang/string_scanner/actions/workflows/test-package.yml)

[![pub package](https://img.shields.io/pub/v/string_scanner.svg)](https://pub.dev/packages/string_scanner)

[![package publisher](https://img.shields.io/pub/publisher/string_scanner.svg)](https://pub.dev/packages/string_scanner/publisher)

This package exposes a `StringScanner` type that makes it easy to parse a string

using a series of `Pattern`s. For example:

```dart

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;

}

```