nweiz@google.com
2eac837fc0
This code has been pulled out of the Shelf package. R=kevmoo@google.com Review URL: https://codereview.chromium.org//213833013 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@34665 260f80e4-7a28-3924-810f-c04153c831b5
38 lines
1.2 KiB
Markdown
38 lines
1.2 KiB
Markdown
This package exposes a `StringScanner` type that makes it easy to parse a string
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using a series of `Pattern`s. For example:
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```dart
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import 'dart:math';
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import 'package:string_scanner/string_scanner.dart';
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num parseNumber(String source) {
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// Scan a number ("1", "1.5", "-3").
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var scanner = new StringScanner(source);
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// [Scanner.scan] tries to consume a [Pattern] and returns whether or not it
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// succeeded. It will move the scan pointer past the end of the pattern.
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var negative = scanner.scan("-");
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// [Scanner.expect] consumes a [Pattern] and throws a [FormatError] if it
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// fails. Like [Scanner.scan], it will move the scan pointer forward.
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scanner.expect(new RegExp(r"\d+"));
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// [Scanner.lastMatch] holds the [MatchData] for the most recent call to
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// [Scanner.scan], [Scanner.expect], or [Scanner.matches].
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var number = int.parse(scanner.lastMatch[0]);
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if (scanner.scan(".")) {
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scanner.expect(new RegExp(r"\d+"));
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var decimal = scanner.lastMatch[0];
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number += int.parse(decimal) / math.pow(10, decimal.length);
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}
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// [Scanner.expectDone] will throw a [FormatError] if there's any input that
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// hasn't yet been consumed.
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scanner.expectDone();
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return (negative ? -1 : 1) * number;
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}
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```
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