added random.DNASequence function. (#179)

Author: TimothyStiles

random/random.go

@@ -5,7 +5,8 @@ import (
 	"math/rand"
 )
 
-// ProteinSequence returns a random protein sequence as a string that have size length, starts with aminoacid M (Methionine) and finishes with * (stop codon). The random generator uses the seed provided as parameter.
+// ProteinSequence returns a random protein sequence string of a given length and seed.
+// All returned sequences start M (Methionine) and end with * (stop codon).
 func ProteinSequence(length int, seed int64) (string, error) {
 	//The length needs to be greater than two because the random protein sequenced returned always contain a start and stop codon. You could see more about this stuff here: https://en.wikipedia.org/wiki/Genetic_code#Start_and_stop_codons
 	if length <= 2 {
@@ -34,3 +35,19 @@ func ProteinSequence(length int, seed int64) (string, error) {
 
 	return string(randomSequence), nil
 }
+
+// DNASequence returns a random DNA sequence string of a given length and seed.
+func DNASequence(length int, seed int64) (string, error) {
+
+	var nucleicAcidsAlphabet = []rune("ACTG")
+	alphabetLength := len(nucleicAcidsAlphabet)
+	rand.Seed(seed)
+
+	randomSequence := make([]rune, length)
+	for basepair := range randomSequence {
+		randomIndex := rand.Intn(alphabetLength)
+		randomSequence[basepair] = nucleicAcidsAlphabet[randomIndex]
+	}
+
+	return string(randomSequence), nil
+}

random/random_test.go

@@ -42,3 +42,10 @@ func TestRandomProteinSequenceError(t *testing.T) {
 		t.Errorf("Random sequence must have sequence size equals 0 'RandomSequence(2, 4)'. Got this: \n%s instead of \n%s", strconv.Itoa(len(sequence)), strconv.Itoa(length))
 	}
 }
+func ExampleDNASequence() {
+	// RandomDNASequence builds a DNA Sequence by only passing through arguments a length and a seed that will be use to generate a randomly the sequence. The length needs to be greater than two because every sequence already have a start and stop codon. Seed makes this test deterministic.
+	randomDNA, _ := DNASequence(15, 2)
+	fmt.Println(randomDNA)
+
+	// Output: TTAAATTAGATGCAA
+}