def check(pattern, **options)
      params, length = create_pattern(pattern, **options).peek_params(rest)
      ScanResult.new(self, @position, length, params) if params
    end
def check(pattern, **options)
      params, length = create_pattern(pattern, **options).peek_params(rest)
      ScanResult.new(self, @position, length, params) if params
    end
Checks if the given pattern matches any substring starting at the current position.

 Does not affect {#position} or {#params}.

 @param (see Mustermann.new)
 @return [Mustermann::StringScanner::ScanResult, nil] the matched substring, nil if it didn't match