# bin/set-bytes Return a copy of `$bytes` with the bytes of `$data` overlaid at `offset`. The copy has the same length as the original — this is an overlay, not an insert. Byte strings are immutable, so the original is unchanged. ## Syntax

[bin/set-bytes $bytes $offset $data]

## Parameters - `$bytes` — byte string to copy and write into - `$offset` — 0-based byte offset - `$data` — bytes to overlay ## Examples

def buf [bin/set-bytes [bin/bytes "AB..CD"] 2 "XY"]
[bytes/len $buf]        # → 6
[str $buf]              # → "ABXYCD"

## Returns New byte string. A negative offset or an overlay that runs past the end returns `%Err{:message}`. ## See Also `bin/set-u8`, `bin/bytes-at`, `bin/bytes`