Transformation of Combs
=======================

Imports
-------

> import FlatCurry as FC
> import AbstractCurry as AC
> import AbstractHaskell

> import SrcRef

Import the converters from flat to abstract curry without any debug
transformation:

> import FlatToAbstractCurry

Import the transformation monad `TM`:

> import TransformationMonad

Import utily and constants for debug information and hooks:

> import TransformationDebugInfo

Import the support for higher order.

> import TransformationPartCalls

Transformation
--------------

Transforms a comb call in the Transformation Monad to get fresh variables.

> transformComb :: CombType -> FC.QName -> [CExpr] -> String -> [SrcRef] -> TM CExpr
> transformComb ct name args mod srcRefs =
>   freshVars (length args) >>=. \vars ->
>   let

  Debug info for the hook, contains current source reference as static info
  and terms of the arguments as dynamic info.

>     info = debugInfo (createStaticInfo mod srcRefs)
>                      (dynamicInfo (presym "[]")
>                                   (list (map genTermCallVar vars)))
>   in

  Delegate to method for comb type taking fresh vars and debug info, too:

>     ret $ transformComb' ct name args vars info

Transformation of specific `CombType`
-------------------------------------

> transformComb' :: CombType -> FC.QName -> [CExpr] -> [VarIndex] -> CExpr -> CExpr

Transform regular function calls with a func call hook and an `eval`.

> transformComb' FuncCall name@(_,fn) args vars info =
>   call (renameFunc name) args vars insertHook
>   where
>     insertHook value = comb (debugMonadAs,"funcCallHook")
>                             [acyStr fn,info,value]

Transforms partly applied functions with a part call hook, wrapped with a
returned `FuncRep`.

> transformComb' (FuncPartCall n) name@(mn,_) args vars _ =

  Use the part call helper for number of missing arguments.
  The helper takes the term representation and the function applied to the
  available arguments (`call`). Uses `id` as wrapper to have the helper call
  the hooks:

>   (call (renameFunc name) args vars pcWrap) 
>     where
>       pcWrap = wrapReturn . helper n funcTerm
>       helper = if n <= arityThreshold
>                then combDefaultPC
>                else combPC mn

  Create the function represention term by calling
  `<module>.term_<function>`
  with generated argument terms:

>       funcTerm     = comb (pcTermName name) [argsTerms]
>       argsTerms    = list (map genTermCallVar vars)

Transform constructor calls with a constructor hook and an wrapped `return`:

> transformComb' ConsCall name args vars info =
>   call (renameCons name) args vars $
>        (insHook "constructor" info) . wrapReturn

A part call of a constructor is transformed similar to `FuncPartCall` using the  corresponding part call helper to return a monadic function.
But a constructor is not monadic, for that reason a lambda term is inserted to handle all arguments and `return` the constructed data.

> transformComb' (ConsPartCall n) name@(mn,_) args vars _ =
>   (callExpr lambda args vars pcWrap) 
>     where
>       lambda    = CLambda lamdaVars combCall
>       missing   = map (+length vars) [0..(n-1)]
>       lamdaVars = map px missing
>       combCall  = wrapReturn $ comb (renameCons name) $ map xx (vars++missing)
>       pcWrap    = wrapReturn . helper n consTerm
>       helper    = if n <= arityThreshold
>                   then combDefaultPC
>                   else combPC mn

  Create the function represention term by calling
  `<module>.term_<Constructor>`
  with generated argument terms:

>       consTerm  = comb (pcConsName name) [argsTerms]
>       argsTerms = list (map genTermCallVar vars)


Creates the comb call for given name, argument expressions and fresh variables.

> call :: FC.QName -> [CExpr] -> [VarIndex] -> (CExpr -> CExpr) -> CExpr
> call name args vars wrapper = callExpr combCall args vars wrapper
>   where combCall = (comb name (map xx vars))


Creates the call for given call expression, argument expressions and fresh variables.
Constants are called directly, a `do` expression is returned for functions and constructors with arguments, evaluating the arguments first.

> callExpr :: CExpr -> [CExpr] -> [VarIndex] -> (CExpr -> CExpr) -> CExpr
> callExpr expr args vars wrapper =
>   if null args

  No arguments, a `do` expression is not required:

>    then wrapper $ expr

  Evaluate all arguments in a `do` with the expression as last expression:

>    else CDoExpr ((zipWith (CSPat . px) vars args) ++ [CSExpr $ wrapper expr])


> funcRep x y = comb funcRepCons [x,y]