feat: add typed mem.set

std/mem/mem.hon

@@ -35,6 +35,12 @@ eql proc($T type, left, right []T) bool {
     return true
 }
 
+#! assign `value` to each slice element, preserving its typed value rather than repeating a byte.
+#! an empty destination is a no-op.
+set proc($T type, destination []mut T, value T) void {
+    for (0..destination.len) |i| destination[i] = value
+}
+
 #! allocate memory for a slice of type `T` with `count` elements.
 alloc proc($T type, allocator Allocator, count usize) []mut T ! AllocError {
     if (count == 0) return empty_slice(T, 0)

std/mem/mem.test.hon

@@ -0,0 +1,24 @@
+import "@std/testing"
+
+@hide:file
+Record :: struct {
+    tag u8
+    id u32
+}
+
+fills_typed_values_within_slice_boundaries test {
+    values [4]mut u32 := [1, 2, 3, 4]
+    set(values[1..3], u32(305419896))
+    set(values[2..2], u32(0))
+    try testing.expect_equal(u32(1), values[0])
+    try testing.expect_equal(u32(305419896), values[1])
+    try testing.expect_equal(u32(305419896), values[2])
+    try testing.expect_equal(u32(4), values[3])
+
+    records [2]mut Record := [Record{ tag = 0, id = 0 }, Record{ tag = 0, id = 0 }]
+    set(records[..], Record{ tag = 3, id = maxval!(u32) })
+    for records |record| {
+        try testing.expect_equal(u8(3), record.tag)
+        try testing.expect_equal(maxval!(u32), record.id)
+    }
+}