Parsec-like expressions to read web service parameters and generate the response

A haskell formlet is the combination of a parameter parser plus a writer to generate HTTP output

I use this similarity to create parsec-like combinators that use the formlet monad in MFlow (the View monad)  to parse the web service parameters and to generate the output.


This service below implements a service that sum or multiply two Int-egers.

main  = runNavigation "apiparser" . step . asks $
             do rest "sum"  ; disp $ (+) <$> wint "t1" <*> wint "t2"
         <|> do rest "prod" ; disp $ (*) <$> wint "t1" <*> wint "t2"
         <?> do -- blaze Html
                h1 << "ERROR. API usage:"
                h3 << "http://server/api/sum?t1=[Int]&t2=[Int]"
                h3 << "http://server/api/prod?t1=[Int]&t2=[Int]"

    where
    asks w= ask $ w >> stop






See a more complete explanation and working examples here:

http://mflowdemo.herokuapp.com/noscript/wiki/webservices




By the way:



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World's longest working applicative and monadic combinator expression ever

at:  http://mflowdemo.herokuapp.com/noscript/wiki/expressionever