From 1d133a2e372b207af6a988528a6a66612ed21398 Mon Sep 17 00:00:00 2001
From: Zack <zack@zacklott.co.uk>
Date: Wed, 26 Apr 2023 07:49:45 +0100
Subject: [PATCH] Catch that the Q in the QGram has to be positive

---
 README.md     |  6 +++++-
 qgram.go      |  4 ++++
 qgram_test.go | 10 ++++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 9f9f407..9bf3e1b 100644
--- a/README.md
+++ b/README.md
@@ -57,4 +57,8 @@ Additional information for this algorithm can be found https://en.wikipedia.org/
 import "github.com/roadsigns/fuzzy"
 
 fuzzy.SorensenDice("elon musk", "colon musk")
-```  
\ No newline at end of file
+```  
+
+### Q-Gram
+The Q-Gram algorithm is a similarity algorithm that It does this by dividing each string into substrings of length Q and then comparing the substrings to determine how many of them are the same in both strings.
+Additional information for this algorithm can be found https://en.wikipedia.org/wiki/N-gram
\ No newline at end of file
diff --git a/qgram.go b/qgram.go
index 8535777..81e16b6 100644
--- a/qgram.go
+++ b/qgram.go
@@ -1,6 +1,10 @@
 package fuzzy
 
 func QGram(source string, target string, q int) float64 {
+	if q <= 0 {
+		return 0.0
+	}
+
 	qGrams1 := generateQGrams(source, q)
 	qGrams2 := generateQGrams(target, q)
 
diff --git a/qgram_test.go b/qgram_test.go
index f7488f1..e1d3222 100644
--- a/qgram_test.go
+++ b/qgram_test.go
@@ -12,6 +12,16 @@ func TestQGram(t *testing.T) {
 	assert.Equal(t, expected, got)
 }
 
+func TestQGramNegativeValue(t *testing.T) {
+	expected := 0.0
+	got := fuzzy.QGram("Fish", "Fish", 0)
+	assert.Equal(t, expected, got)
+
+	expected = 0.0
+	got = fuzzy.QGram("Fish", "Fish", -1)
+	assert.Equal(t, expected, got)
+}
+
 func BenchmarkQGram(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		fuzzy.QGram("John Jones", "Jon Jones", 3)