prevent negative weights in Choice

These should break things (by design), so let's just guard against it at the API interface via type system.

Things are kept internally as ints because most golang stdlib functions expect that, so we can avoid casting everywhere.

Author: mroth

weightedrand.go

@@ -18,7 +18,7 @@ import (
 // Choice is a generic wrapper that can be used to add weights for any object
 type Choice struct {
 	Item   interface{}
-	Weight int
+	Weight uint
 }
 
 // A Chooser caches many possible Choices in a structure designed to improve
@@ -38,7 +38,7 @@ func NewChooser(cs ...Choice) Chooser {
 	totals := make([]int, n, n)
 	runningTotal := 0
 	for i, c := range cs {
-		runningTotal += c.Weight
+		runningTotal += int(c.Weight)
 		totals[i] = runningTotal
 	}
 	return Chooser{data: cs, totals: totals, max: runningTotal}

weightedrand_test.go

@@ -16,7 +16,7 @@ func mockChoices(n int) []Choice {
 	for i := 0; i < n; i++ {
 		s := "⚽️"
 		w := rand.Intn(10)
-		c := Choice{Item: s, Weight: w}
+		c := Choice{Item: s, Weight: uint(w)}
 		choices = append(choices, c)
 	}
 	return choices
@@ -35,7 +35,7 @@ func TestWeightedChoice(t *testing.T) {
 	presorted data. */
 	list := rand.Perm(10)
 	for _, v := range list {
-		c := Choice{Weight: v, Item: v}
+		c := Choice{Weight: uint(v), Item: v}
 		choices = append(choices, c)
 	}
 	t.Log("FYI mocked choices of", choices)
@@ -59,8 +59,8 @@ func TestWeightedChoice(t *testing.T) {
 	for i, c := range choices[0 : len(choices)-1] {
 		next := choices[i+1]
 		cw, nw := c.Weight, next.Weight
-		if !(chosenCount[cw] < chosenCount[nw]) {
-			t.Error("Value not lesser", cw, nw, chosenCount[cw], chosenCount[nw])
+		if !(chosenCount[int(cw)] < chosenCount[int(nw)]) {
+			t.Error("Value not lesser", cw, nw, chosenCount[int(cw)], chosenCount[int(nw)])
 		}
 	}