Make minor refactoring

Signed-off-by: Pavel Korotkov <pavel@nspcc.ru>

connections/sampler.go

@@ -2,26 +2,13 @@ package connections
 
 import "math/rand"
 
-// https://www.keithschwarz.com/darts-dice-coins/
+// See Vose's Alias Method (https://www.keithschwarz.com/darts-dice-coins/).
 type Sampler struct {
 	randomGenerator *rand.Rand
 	probabilities   []float64
 	alias           []int
 }
 
-type workList []int
-
-func (wl *workList) push(e int) {
-	*wl = append(*wl, e)
-}
-
-func (wl *workList) pop() int {
-	l := len(*wl) - 1
-	n := (*wl)[l]
-	*wl = (*wl)[:l]
-	return n
-}
-
 func NewSampler(probabilities []float64, source rand.Source) *Sampler {
 	sampler := &Sampler{}
 	var (
@@ -39,28 +26,28 @@ func NewSampler(probabilities []float64, source rand.Source) *Sampler {
 	}
 	for i, pi := range p {
 		if pi < 1 {
-			small = append(small, i)
+			small.add(i)
 		} else {
-			large = append(large, i)
+			large.add(i)
 		}
 	}
-	for len(large) > 0 && len(small) > 0 {
+	for len(small) > 0 && len(large) > 0 {
-		l, g := small.pop(), large.pop()
+		l, g := small.remove(), large.remove()
 		sampler.probabilities[l] = p[l]
 		sampler.alias[l] = g
-		p[g] = (p[g] + p[l]) - 1
+		p[g] = p[g] + p[l] - 1
 		if p[g] < 1 {
-			small.push(g)
+			small.add(g)
 		} else {
-			large.push(g)
+			large.add(g)
 		}
 	}
 	for len(large) > 0 {
-		g := large.pop()
+		g := large.remove()
 		sampler.probabilities[g] = 1
 	}
 	for len(small) > 0 {
-		l := small.pop()
+		l := small.remove()
 		sampler.probabilities[l] = 1
 	}
 	return sampler
@@ -74,3 +61,16 @@ func (g *Sampler) Next() int {
 	}
 	return g.alias[i]
 }
+
+type workList []int
+
+func (wl *workList) add(e int) {
+	*wl = append(*wl, e)
+}
+
+func (wl *workList) remove() int {
+	l := len(*wl) - 1
+	n := (*wl)[l]
+	*wl = (*wl)[:l]
+	return n
+}