What the heck is a parser-combinator?

Re:What the heck is a parser-combinator? by omaranto on Wednesday June 21, 2017 @12:10PM (#14605017)

Is that really how the term is used? I would have naively thought that among your examples only 'then' and 'thenDependent' are parser combinators, and that 'string("foobar")', 'char', 'always(x)' and 'never' are simply called parsers. (Maybe 'string', as opposed to the evaluated 'string("foobar")', should be called a combinator even though it doesn't take any parsers as arguments...)

Just like I'd call '+' and '*' arithmetic operators but I'd call '3' a number.

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Re:What the heck is a parser-combinator? by tel on Wednesday June 21, 2017 @01:48PM (#14606173)

Combinator is a pretty overloaded term, it's difficult to pin down. In practice, something like `never` would be called a combinator, though.

Also, in theory a combinator is just an expression of no free variables. S-K-I calculus is the canonical set of "combinators" and all three of them could be considered "functions" but also could be considered "atoms". So perhaps it's just vague.

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Re:What the heck is a parser-combinator? by DonaldPShimoda on Wednesday June 21, 2017 @01:00PM (#14605607)

In my experience (limited) yes, this is how the term is used.

"Combinator" != "combiner". A combinator is a thing which is combined with other combinators. When you combine two combinators, you end up with yet another combinator which can be combined with other combinators. Very composable, in the functional spirit of things.

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Re:What the heck is a parser-combinator? by omaranto on Wednesday June 21, 2017 @01:22PM (#14605894)

I'm not so sure, and however wrote the Wikipedia page seems to agree with me. The first sentence is "In computer programming, a parser combinator is a higher-order function that accepts several parsers as input and returns a new parser as its output." Also people name the type something like Parser<A>, not ParserCombinator<A>.

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