Componentified version of http://saml.rilspace.org/calculating-gc-content-in-python-and-d-how-to-get-10x-speedup-in-d

gistfile1.d

import std.stdio;
import std.string;
import std.algorithm;
import std.regex;
import std.traits;
int gcCount = 0;
int totalBaseCount = 0;

void main() {
    File file = File("Homo_sapiens.GRCh37.67.dna_rm.chromosome.Y.fa","r");
    string line = "";

    file.byLine(KeepTerminator.yes).reduce!countGc;
    //map!(a => calcGc(a));
    //calcGc();

    //while (!file.eof()) {
    //    line = chomp(file.readln());
    //    if (!startsWith(line, ">")) {
    //        gcCount = countchars(line, "[GC]");
    //        totalBaseCount += countchars(line, "[GCTA]");
    //    }
    //}
    //float gcFraction = ( cast(float)gcCount / totalBaseCount );
    //writeln( gcFraction * 100 );
}

auto calcGc(T)(T line)  {
    if (!startsWith(line, ">")) {
        gcCount = countchars(line, "[GC]");
        totalBaseCount += countchars(line, "[GCTA]");
    }
    //writeln(line);
    //writeln(typeid(typeof(line)));
    return line;
}