Copyright	Copyright (c) Jordan Woehr 2018
License	BSD
Maintainer	Jordan Woehr
Stability	experimental
Safe Haskell	None
Language	Haskell2010

Data.OpenADT.TH

Description

This module exports template haskell functions for generating tedious boilerplate.

Synopsis

mkVarPattern :: Name -> String -> String -> String -> Q [Dec]

Documentation

mkVarPattern Source #

Arguments

:: Name	The `Name` of the type to create patterns for.
-> String	The label in the variant the constructor will have.
-> String	The name of the fixed pattern.
-> String	The name of the unfixed pattern.
-> Q [Dec]

Create patterns for a variant constructor.

For example, for the type FooF with the constructor FooF':

data FooF a x = FooF' a x
$(mkVarPattern ''FooF "foo" "Foo" "FooF")

A pattern similar to the following will be generated:

pattern FooF :: (OpenAlg r "foo" (FooF a) v) => a -> v -> VarF r v
pattern FooF a v <- VarF (view (Label :: Label "foo") -> Just (FooF' a v))

pattern Foo :: (OpenAlg r "foo" (FooF a) (OpenADT r))
            => a -> OpenADT r -> OpenADT r
  where FooF a v = VarF (IsJust (Label :: Label "foo") (FooF' a v))
pattern Foo  a v = Fix (FooF a v)