# bin/set-u64 Return a copy of `$bytes` with an unsigned 64-bit integer written at `offset` (little-endian). Byte strings are immutable — the original `$bytes` is unchanged. ## Syntax

[bin/set-u64 $bytes $offset $value]

## Parameters - `$bytes` — byte string to copy and write into - `$offset` — 0-based byte offset - `$value` — value to write; clamped to the 64-bit range and truncated toward zero ## Examples

def buf [bin/set-u64 [bin/zeros 8] 0 123456789]
[bin/u64-at $buf 0] # → 123456789
[bin/u8-at $buf 0] # → 21

## Returns New byte string. A negative or out-of-bounds offset returns `%Err{:message}`. ## See Also `bin/u64-at`, `bin/set-u64-be`, `bin/set-bytes`, `bin/bytes`