gistfile1.go

package main

import (
	"bufio"
	"fmt"
	"log"
	"os"
)

const (
	G = rune('G')
	C = rune('C')
	A = rune('A')
	T = rune('T')
)

type Pair struct {
	gc int
	at int
}

func main() {
	file, err := os.Open("./Homo_sapiens.GRCh37.67.dna_rm.chromosome.Y.fa")
	if err != nil {
		log.Fatal(err)
	}

	gc_frac := countFile(false, file)
	fmt.Printf("GC count: %v\n", gc_frac)
}

func countFile(async bool, file *os.File) float64 {

	at := 0
	gc := 0
	scanner := bufio.NewScanner(file)

	for scanner.Scan() {
		tmpAt, tmpGc := count(scanner.Text())
		at += tmpAt
		gc += tmpGc
	}
	return float64(gc) / float64((gc + at))
}

func count(line string) (int, int) {
	at := 0
	gc := 0
	for _, c := range line {
		if c == G || c == C {
			gc++
		}
		if c == A || c == T {
			at++
		}
	}

	return at, gc
}