zet

Parser as Struct with Methods is Great

I realized a bunch of unexpected advantages by encapsulating scan.R inside a Parser struct. Perhaps the biggest is that all PEGN identifiers have a one-to-one mapping with their Parser methods. This allows me to document each one. It also allows the creation of node tree constant integers in the same mark namespace without naming collisions. For example, Tag and p.Tag() are separated.

func (p *Parser) Tag() bool {
	p.S.Scan()
	if p.S.R != '#' {
		p.S.P--
		return false
	}
	beg := p.S.P
	var n int
	for p.ULetter() {
		n++
		if n > 20 {
			p.S.Error(TagTooLong{})
		}
	}
	if n > 0 {
		p.add(Tag, beg)
		return true
	}
	return false
}

Returning boolean from the parsing has also got to be one of the smartest accidental things I did. It means that I can loop over the methods just like s.Scan in the scanner.

for p.ULetter() {
  ...
}

That code gobbles up all the ULetters until it hits something that isn’t one, including end of data. That ability to gobble up a bunch of stuff in a simple for loop really feels great. So glad that worked out.

#golang #coding #tips

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