값 전달과 참조 전달 비교

When you call a function, Zig must get your data inside it. There are two routes: pass the value itself or pass a reference to it. 🚚

By default, primitive arguments are passed by value: the function gets its own copy and cannot change your original.

Because it is a copy, edits inside the function never touch the caller. Your variable outside stays exactly as it was.

Function parameters in Zig are immutable. You cannot reassign a parameter inside the body, which keeps intent clear.

To let a function change your data, pass a pointer with *T. The function then works on your actual value, not a copy.

Inside, you use .* to read or write through the pointer. n.* += 1 updates the value the caller still holds.

At the call site you pass an address using &. Then bump(&count) lets the function modify count in place.

For large structs, copying is wasteful. Passing a const pointer shares the data cheaply without allowing changes.

A *const T lets the function read your data but never write it. You get speed without giving up safety.

A slice like []const u8 carries a pointer plus a length, so passing it shares the underlying data without a full copy.

Pass by value for small, read-only data; pass a pointer when you must mutate or when the data is large.

You want a function to change the caller variable. Which parameter form lets it do that?

Values are copied and cannot change your originals; pointers share them. Use *T to mutate and *const T to read large data fast. 🎯