calculating GC content in Dart

gc.dart

#!/usr/local/dart/dart-sdk/bin/dart

// gc.dart
// cf. http://saml.rilspace.org/moar-languagez-gc-content-in-python-d-fpc-c-and-c

import 'dart:io';
import 'dart:async';

main()
{
  int gcCount = 0;
  int atCount = 0;
  var f = new File("Homo_sapiens.GRCh37.67.dna_rm.chromosome.Y.fa");
  var inputStream = f.openRead();

  inputStream
    .transform(new StringDecoder(Encoding.ASCII))
    .transform(new LineTransformer())
    .listen(
      (String line) {
        if (line.startsWith(">")) {
          return;
        }

        int lineLen = line.length;
        for (var i = 0; i < lineLen; ++i) {     // for each char in line
          switch (line[i]) {
            case 'G':
            case 'C':
              gcCount += 1;
              break;
            case 'A':
            case 'T':
              atCount += 1;
              break;
          }
        }
      },
      onDone: () { print(gcCount * 100 / (gcCount + atCount)); },
      onError: (e) { print(e.toString()); });
}

// eof	vim:set syntax=dart shiftwidth=2 expandtab: