Function mapR

mapR<TToken, TOptions, TValue1, TValue2>(
    p: Parser<TToken, TOptions, TValue1>,
    mapper: (
        m: Match<TValue1>,
        data: Data<TToken, TOptions>,
        i: number,
    ) => Result<TValue2>,
): Parser<TToken, TOptions, TValue2>
Make a new parser that transforms the match from a given parser to any Result.

This version can discard a Match - return a NonMatch instead.

Note: pay attention to the return type and indices.

Use map if mapping exists for all matched values.

Use filter for discarding some matches based on a condition, without modifying.
Type Parameters
- TToken
- TOptions
- TValue1
- TValue2
Parameters
- p: Parser<TToken, TOptions, TValue1>
  A base parser.
- mapper: (m: Match<TValue1>, data: Data<TToken, TOptions>, i: number) => Result<TValue2>
  A function that modifies the match.
  - (m: Match<TValue1>, data: Data<TToken, TOptions>, i: number): Result<TValue2>
    Parameters
    m: Match<TValue1>
    A Match object from the base parser (contains the value and the position after the match).
    
    data: Data<TToken, TOptions>
    Data object (tokens and options).
    
    i: number
    Parser position in the tokens array (before the first parser matched).
    
    Returns Result<TValue2>
    A transformed Result object - either Match or NonMatch.
Returns Parser<TToken, TOptions, TValue2>