Jun 10, 2019 · It is true that Parsec has chainl and chainr to parse chains of either left-associative or right-associative operations (i.e. a -> a -> a). So I could quite easily parse something like x + y ...

Jan 26, 2012 · You should use Parsec.Expr.buildExprParser; it is ideal for this purpose. You simply describe your operators, their precedence and associativity, and how to parse an atom, and the combinator builds the parser for you!

Aug 6, 2019 · Unfortunately lambda is not suitable for building a parsec Parser this way since you need to return a parsec.Value type not a boolean, so it will quickly lose its terseness. The design of parsec requires a Parser to act independently on an input stream without knowledge of any other Parser. To do this effectively a Parser must manage an index ...

Jun 4, 2024 · It might seem that this question is a duplicate of this question, however either Parsec or the Indent library has changed since 2012 and none of the old examples I have found for the indent library ...

Nov 16, 2013 · We can see this in action by looking at the code for Parsec directly, which is somewhat more complex than my notion of Parser above. First we examine ParsecT. newtype ParsecT s u m a = ParsecT {unParser :: forall b .

Oct 19, 2021 · There might be several reasons for these two errors, however the Parsec docs does not give possible solutions. In my case going to App & Features > Optional Features > Add Feature and then look for Media Feature Pack and install it, reboot and should work.

Feb 21, 2011 · My understanding is that Parsec creates a nice DSL of writing parsers and Haskell makes it very easy and expressive. But parsing is such a standard/popular technology that deserves its own language, which outputs to multiple target languages. So when shall we use Parsec instead of, say, generating Haskell code from Bison/Antlr?

Sep 19, 2013 · sepEndBy in Parsec does what you want - splits input into a list of parsed entities separated by a given separator, optionally ending with it or eof. Your grammar for line permits the parser to produce a never-ending stream of lines for any input. This can be resolved by making the decision about newline externally to line:

Feb 28, 2012 · I've been working with parsec and I have trouble debugging my code. For example, I can set a breakpoint in ghci, but I'm not sure how to see how much of the input has been consumed, or things like ...

Sep 29, 2015 · Parsec does a very good job as a parsing library and it is a credit to the design that it can be mangled into doing lexical analysis, but for all but small and simple projects it will quickly become unwieldy. I now use alex to create a linear set of tokens and then Parsec turns them into an AST.