37 lines
969 B
Dart
37 lines
969 B
Dart
import 'dart:io';
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import 'package:combinator/combinator.dart';
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import 'package:string_scanner/string_scanner.dart';
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final Parser minus = match('-');
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final Parser<int> digit =
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match(new RegExp(r'[0-9]'), errorMessage: 'Expected a number');
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final Parser digits = digit.plus();
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final Parser dot = match('.');
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final Parser decimal = ( // digits, (dot, digits)?
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digits & (dot & digits).opt() //
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);
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final Parser number = //
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(minus.opt() & decimal) // minus?, decimal
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.map<num>((r) => num.parse(r.span!.text));
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main() {
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while (true) {
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stdout.write('Enter a number: ');
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var line = stdin.readLineSync()!;
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var scanner = new SpanScanner(line, sourceUrl: 'stdin');
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var result = number.parse(scanner)!;
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if (!result.successful) {
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for (var error in result.errors) {
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stderr.writeln(error.toolString);
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stderr.writeln(error.span!.highlight(color: true));
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}
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} else
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print(result.value);
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}
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}
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