@lang:str.charset

Check whether every byte of a string is in a character class (ranges like a-z0-9-; a leading or trailing dash is the literal -).

Returns: bool

Syntax

@lang:str.charset(value class)

Arguments

Name	Type	Description
`value`	`string`	String to check
`class`	`string`	Allowed characters and ranges, e.g. `a-z0-9-` (a leading or trailing dash is the literal `-`)

On-chain face (@str.charset!)

Whether every byte of the string return of a call is in a character class, checked on-chain — only-lowercase is @str.charset!(call a-z).

Examples

load lang

set $token 0x44fA8E6f47987339850636F88629646662444217

# The symbol contains only lowercase letters
assert @str.charset!($token::{symbol()(string)} "a-z") == true

# An ENS-label-ish name: lowercase, digits and dashes
assert @str.charset!($token::{name()(string)} "a-z0-9-") == true

Notes

The class is characters and x-y ranges; a leading or trailing dash is the literal -. It compiles to a 256-bit byte bitmap at build time — the on-chain check is one bit test per byte.
Byte-level: multi-byte UTF-8 characters (every byte ≥ 0x80) fail any ASCII-only class, so a-z really means lowercase ASCII.
The empty string passes every class — pair with @len!(call) > 0 when the value must also be non-empty.
Boolean-valued: usable bare, compared with == true / == false, or nested inside @bool!(...) logic.