belatuk_combinator 5.4.0

belatuk_combinator: ^5.4.0 copied to clipboard

example/main.dart

import 'dart:io';
import 'package:belatuk_combinator/belatuk_combinator.dart';
import 'package:string_scanner/string_scanner.dart';

final Parser minus = match('-');

final Parser<int> digit = match(
  RegExp(r'[0-9]'),
  errorMessage: 'Expected a number',
);

final Parser digits = digit.plus();

final Parser dot = match('.');

final Parser decimal =
    ( // digits, (dot, digits)?
    digits &
    (dot & digits)
        .opt() //
        );

final Parser number = //
    (minus.opt() & decimal) // minus?, decimal
        .map<num>((r) => num.parse(r.span!.text));

void main() {
  while (true) {
    stdout.write('Enter a number: ');
    var line = stdin.readLineSync()!;
    var scanner = SpanScanner(line, sourceUrl: 'stdin');
    var result = number.parse(scanner);

    if (!result.successful) {
      for (var error in result.errors) {
        stderr.writeln(error.toolString);
        stderr.writeln(error.span!.highlight(color: true));
      }
    } else {
      print(result.value);
    }
  }
}