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definition:
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generatorShow :: FunctionGenerator
generatorShow typedecl =
return $ zipWith (forCons (rwBaseModuleName rwNaming, "showRW")) [0..] tcs
where
tcs = typeCons typedecl
forCons wfn i (CCons name _ tes) =
CRule (lhs name tes)
(CSimpleRhs (tupleExpr [CVar (length tes, "strs" ++ show (length tes)), outputExpr]) wheres)
where
outputExpr | length tcs == 1 && null tes = CApply (CSymbol ("Prelude", "showString")) (string2ac "")
| otherwise = applyExpr $ optimizeSingleConstructor tcs (outputConstr : rest)
outputConstr | length tcs <= length coding = applyF ("Prelude", "showChar") [cChar (coding !! i)]
| otherwise = applyF ("Prelude", "showString") [string2ac (codingI i (length tcs))]
rest = map (\index -> CVar (index, "show" ++ show (index + 1))) (fromIndex0 tes)
wheres = map (\rn -> CLocalPat (
tuplePattern [CPVar (rn + 1, "strs" ++ show (rn + 1)), CPVar (rn + 1 + length tes, "show" ++ show (rn+1))]
) (
CSimpleRhs (applyF wfn [CVar (0, "params"), CVar (rn, "strs" ++ show rn), CVar (rn + length tes, varName rn ++ "'")]) []
)) (fromIndex0 tes)
lhs name tes = [ paramsPat
, CPVar (0, "strs0")
, CPComb name (map (\index -> CPVar (index + (length tes + 1), varName index ++ "'")) (fromIndex0 tes))]
where
paramsPat | null tes = anonPattern
| otherwise = CPVar (0, "params")
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documentation:
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--- `showRW` generator implementation.
---
--- For a data definition
---
--- data T a b ... = ConsA | ConsB p_1 ... p_n | ...
---
--- this function generates the following code:
---
--- showRW _ strs_0 ConsA = (strs_0, showChar '0')
--- showRW params strs_0 (ConsB a b ...) = (strs_n, showChar '1' . show_1 . show_2 . ... . show_n)
--- where
--- (strs_1, show_1) = showRW params strs_0 a'
--- (strs_2, show_2) = showRW params strs_1 b'
--- ...
--- (strs_n, show_n) = showRW params strs_{n-1} n'
--- ...
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