# index-of Find a substring in a string, or a value in a list. The string result is a CODEPOINT index — the same coordinate system as `len`/`slice`/`nth` (slice the hit with `$s($i .. ($i + n))`). Returns -1 (strings) or nil (lists) when not found. ## Syntax

[index-of $s $substr]

## Examples

[index-of "a中b文c" "文"]  # 3  (characters: a 中 b 文 → index 3)
[index-of "hello" "z"]     # -1

## Returns Number, or -1/nil when absent. ## See Also `slice`, `in?`, `re/find`