From cd509e9acdda499ef3f998d7b4b93a7cb9dea481 Mon Sep 17 00:00:00 2001
From: Michael Thomson <michael@michaelthomson.dev>
Date: Sat, 25 May 2024 01:29:58 -0400
Subject: [PATCH] arrays-slices

---
 arrays/sum.go      | 32 +++++++++++++++++++++++++++++++
 arrays/sum_test.go | 48 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+)
 create mode 100644 arrays/sum.go
 create mode 100644 arrays/sum_test.go

diff --git a/arrays/sum.go b/arrays/sum.go
new file mode 100644
index 0000000..9a5e702
--- /dev/null
+++ b/arrays/sum.go
@@ -0,0 +1,32 @@
+package main
+
+func Sum(numbers []int) int {
+  sum := 0
+  for _, number := range numbers {
+    sum += number
+  }
+  return sum
+}
+
+func SumAll(numbersToSum ...[]int) []int {
+  var sums []int
+  
+  for _, numbers := range numbersToSum {
+    sums = append(sums, Sum(numbers))
+  }
+
+  return sums
+}
+
+func SumAllTails(numbersToSum ...[]int) []int {
+  var sums []int
+  for _, numbers := range numbersToSum {
+    if len(numbers) == 0 {
+      sums = append(sums, 0)
+    } else {
+      tail := numbers[1:]
+      sums = append(sums, Sum(tail))
+    }
+  }
+  return sums
+}
diff --git a/arrays/sum_test.go b/arrays/sum_test.go
new file mode 100644
index 0000000..c5f8d04
--- /dev/null
+++ b/arrays/sum_test.go
@@ -0,0 +1,48 @@
+package main
+
+import (
+	"slices"
+	"testing"
+)
+
+func TestSum(t *testing.T) {
+  t.Run("collection of 5 numbers", func(t *testing.T) {
+    numbers := []int{1, 2, 3, 4, 5}
+
+    got := Sum(numbers)
+    want := 15
+
+    if got != want {
+      t.Errorf("got %d want %d given, %v", got, want, numbers)
+    }
+  })
+}
+
+func TestSumAll(t *testing.T) {
+  got := SumAll([]int{1, 2}, []int{0, 9})
+  want := []int{3, 9}
+
+  if !slices.Equal(got, want) {
+    t.Errorf("got %v want %v", got, want)
+  }
+}
+
+func TestSumAllTails(t *testing.T) {
+  checkSums := func(t testing.TB, got, want []int) {
+    t.Helper()
+    if !slices.Equal(got, want) {
+      t.Errorf("got %v want %v", got, want)
+    }
+  }
+
+  t.Run("make the sums of some slices", func(t *testing.T) {
+    got := SumAllTails([]int{1, 2}, []int{0, 9})
+    want := []int{2, 9}
+    checkSums(t, got, want)
+  })
+  t.Run("safely sum empty slices", func(t *testing.T) {
+    got := SumAllTails([]int{}, []int{3, 4, 5})
+    want := []int{0, 9}
+    checkSums(t, got, want)
+  })
+}