/*
Package dna implements various DNA analyzing functions.
*/
package dna
import "errors"
// Histogram is a mapping from nucleotide to its count in given DNA.
type Histogram map[rune]int
// DNA is a series of nucleotides.
type DNA string
// Counts generates a histogram of valid nucleotides in the given DNA.
// Returns an error if d contains an invalid nucleotide.
func (d DNA) Counts() (Histogram, error) {
	var hist = Histogram{
		'A': 0,
		'G': 0,
		'C': 0,
		'T': 0,
	}
	for _, nucleotide := range d {
		_, exists := hist[nucleotide]
		if !exists {
			return hist, errors.New("Unrecognized nucleotide")
		}
		hist[nucleotide]++
	}
	return hist, nil
}