I'm trying to learn how to parse files with Pipes, using Pipes.Aeson and Pipes.Parse. I'm a bit bewildered by the library - it seems quite complex, and I couldn't find too many examples of how it should be used.
For example: I have a file containing several JSON objects all of the same type. I'd like to read them into my program one-at-a-time and reduce them down to some value. >From the documentation it looks like I should be using foldAll to do this. foldAll returns a Parser. However, the decode function in Pipes.Aeson has the type decode :: (Monad m, FromJSON a) => Parser ByteString m (Either DecodingError a) so it also returns a Parser. I've written my own function that extracts a field from a parsed JSON object, which has type :: Parser ByteString IO (Either DecodingError Double), and a second function of type :: Parser Double IO Double (and body foldAll max 0 id). Is it possible to compose these into a single parser of type :: Parser ByteString IO (Either DecodingError Double)? The intention being that I extract the field from all the objects in the file, then find the maximum. Eventually I want to be able to run evalStateT on a Parser and a Producer, but I'm having difficulties creating the Parser. I'm sure this either has a really simple solution or I'm approaching it in the wrong way. While I'm here - are there any good resources or projects I can read through that have used the Pipes.Parse (and maybe Pipes.Aeson) library? It'd be helpful to see what idiomatic usage of the libraries looks like. -- You received this message because you are subscribed to the Google Groups "Haskell Pipes" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected].
