From 6b5a35e4ff3d2a18eb21be4656eeaa6812e223f1 Mon Sep 17 00:00:00 2001
From: ntrel <ntrel@noreply.codeberg.org>
Date: Sun, 11 Oct 2026 19:02:13 +0200
Subject: [PATCH] Update doc/langref/test_for.zig (#37181)

Use -1 element instead of 0, as 0 wouldn't affect sum.
Fix 'reslice' wording as example is an array, not a slice.
Increase slice length to 2 to demonstrate feature better.
Split out "for ranges" test from basics with shorter array.
Use usize sum to avoid cast.
Improve comments.
Reuse sum vars.

Reviewed-on: https://codeberg.org/ziglang/zig/pulls/37181
Reviewed-by: Andrew Kelley <andrew@ziglang.org>
---
 doc/langref/test_for.zig | 42 +++++++++++++++++++++++-----------------
 1 file changed, 24 insertions(+), 18 deletions(-)

diff --git a/doc/langref/test_for.zig b/doc/langref/test_for.zig
index d2d40db58fda67705cb38ec234e595ded20d86a5..24c6fe713232c4db3bf63088db184595e87b7d23 100644
--- a/doc/langref/test_for.zig
+++ b/doc/langref/test_for.zig
@@ -1,41 +1,47 @@
 const expectEqual = @import("std").testing.expectEqual;
 
 test "for basics" {
-    const items = [_]i32{ 4, 5, 3, 4, 0 };
+    const items = [_]i32{ 4, 5, 3, -1, 4 };
     var sum: i32 = 0;
 
     // For loops iterate over slices and arrays.
     for (items) |value| {
         // Break and continue are supported.
-        if (value == 0) {
+        if (value < 0) {
             continue;
         }
         sum += value;
     }
     try expectEqual(16, sum);
 
-    // To iterate over a portion of a slice, reslice.
-    for (items[0..1]) |value| {
+    // Use slicing to iterate over a portion of a slice or array.
+    sum = 0;
+    for (items[0..2]) |value| {
         sum += value;
     }
-    try expectEqual(20, sum);
+    try expectEqual(9, sum);
+}
 
-    // To access the index of iteration, specify a second condition as well
-    // as a second capture value.
-    var sum2: i32 = 0;
-    for (items, 0..) |_, i| {
+test "for ranges" {
+    const items = [_]u8{1, 2, 3};
+    var sum: usize = 0;
+
+    // To access the index of iteration, specify an unbounded range as the
+    // second condition, as well as a second capture value.
+    for (items, 0..) |e, i| {
         try expectEqual(usize, @TypeOf(i));
-        sum2 += @as(i32, @intCast(i));
+        sum += i; 
+        try expectEqual(e, i + 1);
     }
-    try expectEqual(10, sum2);
+    try expectEqual(3, sum); // 0 + 1 + 2
 
-    // To iterate over consecutive integers, use the range syntax.
-    // Unbounded range is always a compile error.
-    var sum3: usize = 0;
+    // To iterate over consecutive integers, use bounded range syntax.
+    // A lone unbounded range is a compile error.
+    sum = 0;
     for (0..5) |i| {
-        sum3 += i;
+        sum += i;
     }
-    try expectEqual(10, sum3);
+    try expectEqual(10, sum);
 }
 
 test "multi object for" {
@@ -44,8 +50,8 @@ test "multi object for" {
     var count: usize = 0;
 
     // Iterate over multiple objects.
-    // All lengths must be equal at the start of the loop, otherwise detectable
-    // illegal behavior occurs.
+    // All bounded objects must have equal lengths.
+    // There must be at least one bounded object.
     for (items, items2) |i, j| {
         count += i + j;
     }
-- 
2.54.0