not

not(p: Parser, m?: string): Parser

Applies a parser and succeeds without consuming input if that parser fails.

not cannot feasibly produce an automatic error message on failure. To add an error message, pass an expected error message in as the second argument.

Example

const parser = not(digit())

const s = parse(parser, 'a')
console.log(status(s))  // "ok"
console.log(success(s)) // null

const f = parse(parser, '1')
console.log(status(f))  // "fail"
console.log(failure(f)) // Parse error at (line 1, column 1):
                        //
                        // 1
                        // ^
                        // Unknown message(s)

Parameters

• p: The parser to apply. If it fails, not succeeds.
• m: The optional expected message that will be added if not fails.

Success

• Succeeds if p fails or fails fatally. Does not consume input or return a result.

Failure

• Fails if p succeeds. No input is consumed and the state is not changed.

Throws

• Throws an error if p is not a parser.
• Throws an error if m exists and is not a string.

See Also

• Parser
• empty