Add new SpanScanner.within() and new character scanning methods.
Add StringScanner.scanChar() and .expectChar().

R=jmesserly@google.com

Review URL: https://codereview.chromium.org//2041813002 .
7 files changed
tree: cbde1bd73276833b2102289cd3cdca063868d342
  1. .analysis_options
  2. .gitignore
  3. .test_config
  4. CHANGELOG.md
  5. LICENSE
  6. README.md
  7. codereview.settings
  8. lib/
  9. pubspec.yaml
  10. test/
README.md

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

import 'dart:math';

import 'package:string_scanner/string_scanner.dart';

num parseNumber(String source) {
  // Scan a number ("1", "1.5", "-3").
  var scanner = new 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.
  var 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(new RegExp(r"\d+"));

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

  if (scanner.scan(".")) {
    scanner.expect(new RegExp(r"\d+"));
    var 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;
}