When combining two parsers, for example in a sequence like pSeq in this website, you need to think about what to do with their return values. One approach is to put all return values in a tuple. So lets say we are combining parsers p1,p2,..., p_n in a sequence, then the return value of the parser created by pSeq(p1,p2,...,p_n) is (R(p1), R(p2), ..., R(p_n)) if R(p) is the return value of parser p.

When writing parsers you will often use multiple nested combinators. This means you have nested tuples. Getting the values out of these means "unwrapping" these tuples. Additionally you might not need all of the values in the sequence, some of them might only be for parsing whitespace. So when using the results of the parsers to construct values you have to ignore them. This can for example be done by "mapping" the resulting tuples and only leaving relevant fields. There are other approaches as well, for example chaining parsers with p1.then_ignore(p2) which only returns R(p1).

Maybe I could have chosen the words here a bit better, I hope this makes it more clear what I mean.

I have also tried making a side-by-side comparison of parsers for grammars being written using my library and others, maybe this can act as an example: https://blog.arnedebo.com/posts/a-grammar-first-approach-to-...

I’ve always used parser combinaties in Haskell and I’ve never seen the things you describe. I guess in Haskell one always directly apply the parts to the function you want (ie an AST node constructor).

Does your language have native tuple destructuring syntax?

The ignore example is just p1 <* p2 in Haskell (that operator is in the standard library).

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