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{-# LANGUAGE TemplateHaskell, QuasiQuotes #-} |
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|
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{-| TemplateHaskell helper for HTools. |
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|
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As TemplateHaskell require that splices be defined in a separate |
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module, we combine all the TemplateHaskell functionality that HTools |
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needs in this module (except the one for unittests). |
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|
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-} |
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|
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{- |
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|
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Copyright (C) 2011 Google Inc. |
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|
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This program is free software; you can redistribute it and/or modify |
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it under the terms of the GNU General Public License as published by |
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the Free Software Foundation; either version 2 of the License, or |
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(at your option) any later version. |
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|
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This program is distributed in the hope that it will be useful, but |
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WITHOUT ANY WARRANTY; without even the implied warranty of |
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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General Public License for more details. |
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|
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You should have received a copy of the GNU General Public License |
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along with this program; if not, write to the Free Software |
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
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02110-1301, USA. |
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|
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-} |
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|
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module Ganeti.THH ( declareSADT |
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, makeJSONInstance |
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, genOpID |
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, genOpCode |
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, noDefault |
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) where |
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|
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import Control.Monad (liftM) |
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import Data.Char |
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import Data.List |
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import Language.Haskell.TH |
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|
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import qualified Text.JSON as JSON |
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|
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-- * Helper functions |
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|
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-- | Ensure first letter is lowercase. |
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-- |
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-- Used to convert type name to function prefix, e.g. in @data Aa -> |
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-- aaToString@. |
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ensureLower :: String -> String |
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ensureLower [] = [] |
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ensureLower (x:xs) = toLower x:xs |
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|
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-- | Helper for quoted expressions. |
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varNameE :: String -> Q Exp |
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varNameE = varE . mkName |
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|
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-- | showJSON as an expression, for reuse. |
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showJSONE :: Q Exp |
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showJSONE = varNameE "showJSON" |
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|
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-- | ToString function name. |
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toStrName :: String -> Name |
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toStrName = mkName . (++ "ToString") . ensureLower |
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|
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-- | FromString function name. |
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fromStrName :: String -> Name |
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fromStrName = mkName . (++ "FromString") . ensureLower |
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|
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-- | Converts a name to it's varE/litE representations. |
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-- |
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reprE :: Either String Name -> Q Exp |
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reprE = either stringE varE |
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|
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-- * Template code for simple string-equivalent ADTs |
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|
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-- | Generates a data type declaration. |
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-- |
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-- The type will have a fixed list of instances. |
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strADTDecl :: Name -> [String] -> Dec |
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strADTDecl name constructors = |
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DataD [] name [] |
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(map (flip NormalC [] . mkName) constructors) |
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[''Show, ''Read, ''Eq, ''Enum, ''Bounded, ''Ord] |
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|
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-- | Generates a toString function. |
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-- |
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-- This generates a simple function of the form: |
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-- |
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-- @ |
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-- nameToString :: Name -> String |
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-- nameToString Cons1 = var1 |
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-- nameToString Cons2 = \"value2\" |
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-- @ |
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genToString :: Name -> Name -> [(String, Either String Name)] -> Q [Dec] |
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genToString fname tname constructors = do |
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sigt <- [t| $(conT tname) -> String |] |
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-- the body clauses, matching on the constructor and returning the |
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-- string value |
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clauses <- mapM (\(c, v) -> clause [recP (mkName c) []] |
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(normalB (reprE v)) []) constructors |
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return [SigD fname sigt, FunD fname clauses] |
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|
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-- | Generates a fromString function. |
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-- |
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-- The function generated is monadic and can fail parsing the |
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-- string. It is of the form: |
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-- |
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-- @ |
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-- nameFromString :: (Monad m) => String -> m Name |
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-- nameFromString s | s == var1 = Cons1 |
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-- | s == \"value2\" = Cons2 |
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-- | otherwise = fail /.../ |
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-- @ |
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genFromString :: Name -> Name -> [(String, Name)] -> Q [Dec] |
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genFromString fname tname constructors = do |
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-- signature of form (Monad m) => String -> m $name |
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sigt <- [t| (Monad m) => String -> m $(conT tname) |] |
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-- clauses for a guarded pattern |
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let varp = mkName "s" |
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varpe = varE varp |
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clauses <- mapM (\(c, v) -> do |
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-- the clause match condition |
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g <- normalG [| $varpe == $(varE v) |] |
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-- the clause result |
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r <- [| return $(conE (mkName c)) |] |
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return (g, r)) constructors |
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-- the otherwise clause (fallback) |
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oth_clause <- do |
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g <- normalG [| otherwise |] |
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r <- [|fail ("Invalid string value for type " ++ |
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$(litE (stringL (nameBase tname))) ++ ": " ++ $varpe) |] |
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return (g, r) |
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let fun = FunD fname [Clause [VarP varp] |
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(GuardedB (clauses++[oth_clause])) []] |
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return [SigD fname sigt, fun] |
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|
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-- | Generates a data type from a given string format. |
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-- |
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-- The format is expected to multiline. The first line contains the |
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-- type name, and the rest of the lines must contain two words: the |
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-- constructor name and then the string representation of the |
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-- respective constructor. |
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-- |
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-- The function will generate the data type declaration, and then two |
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-- functions: |
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-- |
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-- * /name/ToString, which converts the type to a string |
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-- |
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-- * /name/FromString, which (monadically) converts from a string to the type |
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-- |
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-- Note that this is basically just a custom show/read instance, |
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-- nothing else. |
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declareSADT :: String -> [(String, Name)] -> Q [Dec] |
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declareSADT sname cons = do |
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let name = mkName sname |
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ddecl = strADTDecl name (map fst cons) |
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-- process cons in the format expected by genToString |
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cons' = map (\(a, b) -> (a, Right b)) cons |
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tostr <- genToString (toStrName sname) name cons' |
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fromstr <- genFromString (fromStrName sname) name cons |
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return $ ddecl:tostr ++ fromstr |
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|
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|
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-- | Creates the showJSON member of a JSON instance declaration. |
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-- |
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-- This will create what is the equivalent of: |
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-- |
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-- @ |
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-- showJSON = showJSON . /name/ToString |
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-- @ |
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-- |
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-- in an instance JSON /name/ declaration |
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genShowJSON :: String -> Q [Dec] |
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genShowJSON name = [d| showJSON = JSON.showJSON . $(varE (toStrName name)) |] |
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|
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-- | Creates the readJSON member of a JSON instance declaration. |
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-- |
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-- This will create what is the equivalent of: |
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-- |
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-- @ |
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-- readJSON s = case readJSON s of |
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-- Ok s' -> /name/FromString s' |
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-- Error e -> Error /description/ |
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-- @ |
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-- |
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-- in an instance JSON /name/ declaration |
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genReadJSON :: String -> Q Dec |
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genReadJSON name = do |
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let s = mkName "s" |
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body <- [| case JSON.readJSON $(varE s) of |
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JSON.Ok s' -> $(varE (fromStrName name)) s' |
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JSON.Error e -> |
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JSON.Error $ "Can't parse string value for type " ++ |
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$(stringE name) ++ ": " ++ e |
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|] |
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return $ FunD (mkName "readJSON") [Clause [VarP s] (NormalB body) []] |
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|
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-- | Generates a JSON instance for a given type. |
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-- |
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-- This assumes that the /name/ToString and /name/FromString functions |
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-- have been defined as by the 'declareSADT' function. |
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makeJSONInstance :: Name -> Q [Dec] |
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makeJSONInstance name = do |
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let base = nameBase name |
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showJ <- genShowJSON base |
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readJ <- genReadJSON base |
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return [InstanceD [] (AppT (ConT ''JSON.JSON) (ConT name)) (readJ:showJ)] |
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|
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-- * Template code for opcodes |
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|
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-- | Transforms a CamelCase string into an_underscore_based_one. |
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deCamelCase :: String -> String |
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deCamelCase = |
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intercalate "_" . map (map toUpper) . groupBy (\_ b -> not $ isUpper b) |
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|
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-- | Computes the name of a given constructor |
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constructorName :: Con -> Q Name |
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constructorName (NormalC name _) = return name |
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constructorName (RecC name _) = return name |
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constructorName x = fail $ "Unhandled constructor " ++ show x |
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|
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-- | Builds the constructor-to-string function. |
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-- |
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-- This generates a simple function of the following form: |
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-- |
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-- @ |
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-- fname (ConStructorOne {}) = "CON_STRUCTOR_ONE" |
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-- fname (ConStructorTwo {}) = "CON_STRUCTOR_TWO" |
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-- @ |
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-- |
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-- This builds a custom list of name/string pairs and then uses |
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-- 'genToString' to actually generate the function |
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genOpID :: Name -> String -> Q [Dec] |
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genOpID name fname = do |
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TyConI (DataD _ _ _ cons _) <- reify name |
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cnames <- mapM (liftM nameBase . constructorName) cons |
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let svalues = map (Left . deCamelCase) cnames |
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genToString (mkName fname) name $ zip cnames svalues |
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|
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|
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-- | OpCode parameter (field) type |
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type OpParam = (String, Q Type, Q Exp) |
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|
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-- | Generates the OpCode data type. |
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-- |
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-- This takes an opcode logical definition, and builds both the |
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-- datatype and the JSON serialisation out of it. We can't use a |
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-- generic serialisation since we need to be compatible with Ganeti's |
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-- own, so we have a few quirks to work around. |
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-- |
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-- There are three things to be defined for each parameter: |
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-- |
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-- * name |
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-- |
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-- * type; if this is 'Maybe', will only be serialised if it's a |
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-- 'Just' value |
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-- |
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-- * default; if missing, won't raise an exception, but will instead |
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-- use the default |
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-- |
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genOpCode :: String -- ^ Type name to use |
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-> [(String, [OpParam])] -- ^ Constructor name and parameters |
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-> Q [Dec] |
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genOpCode name cons = do |
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decl_d <- mapM (\(cname, fields) -> do |
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-- we only need the type of the field, without Q |
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fields' <- mapM (\(_, qt, _) -> |
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qt >>= \t -> return (NotStrict, t)) |
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fields |
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return $ NormalC (mkName cname) fields') |
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cons |
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let declD = DataD [] (mkName name) [] decl_d [''Show, ''Read, ''Eq] |
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|
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(savesig, savefn) <- genSaveOpCode cons |
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(loadsig, loadfn) <- genLoadOpCode cons |
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return [declD, loadsig, loadfn, savesig, savefn] |
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|
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-- | Checks whether a given parameter is options |
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-- |
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-- This requires that it's a 'Maybe'. |
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isOptional :: Type -> Bool |
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isOptional (AppT (ConT dt) _) | dt == ''Maybe = True |
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isOptional _ = False |
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-- | Generates the \"save\" expression for a single opcode parameter. |
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-- |
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-- There is only one special handling mode: if the parameter is of |
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-- 'Maybe' type, then we only save it if it's a 'Just' value, |
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-- otherwise we skip it. |
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saveField :: Name -- ^ The name of variable that contains the value |
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-> OpParam -- ^ Parameter definition |
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-> Q Exp |
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saveField fvar (fname, qt, _) = do |
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t <- qt |
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let fnexp = stringE fname |
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fvare = varE fvar |
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(if isOptional t |
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then [| case $fvare of |
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Just v' -> [( $fnexp, $showJSONE v')] |
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Nothing -> [] |
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|] |
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else [| [( $fnexp, $showJSONE $fvare )] |]) |
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|
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-- | Generates the \"save\" clause for an entire opcode constructor. |
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-- |
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-- This matches the opcode with variables named the same as the |
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-- constructor fields (just so that the spliced in code looks nicer), |
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-- and passes those name plus the parameter definition to 'saveField'. |
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saveConstructor :: String -- ^ The constructor name |
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-> [OpParam] -- ^ The parameter definitions for this |
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-- constructor |
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-> Q Clause -- ^ Resulting clause |
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saveConstructor sname fields = do |
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let cname = mkName sname |
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let fnames = map (\(n, _, _) -> mkName n) fields |
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let pat = conP cname (map varP fnames) |
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let felems = map (uncurry saveField) (zip fnames fields) |
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-- now build the OP_ID serialisation |
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opid = [| [( $(stringE "OP_ID"), |
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$showJSONE $(stringE . deCamelCase $ sname) )] |] |
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flist = listE (opid:felems) |
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-- and finally convert all this to a json object |
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flist' = [| $(varNameE "makeObj") (concat $flist) |] |
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clause [pat] (normalB flist') [] |
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|
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-- | Generates the main save opcode function. |
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-- |
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-- This builds a per-constructor match clause that contains the |
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-- respective constructor-serialisation code. |
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genSaveOpCode :: [(String, [OpParam])] -> Q (Dec, Dec) |
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genSaveOpCode opdefs = do |
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cclauses <- mapM (uncurry saveConstructor) opdefs |
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let fname = mkName "saveOpCode" |
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sigt <- [t| $(conT (mkName "OpCode")) -> JSON.JSValue |] |
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return $ (SigD fname sigt, FunD fname cclauses) |
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|
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-- | Generates the \"load\" field for a single parameter. |
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-- |
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-- There is custom handling, depending on how the parameter is |
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-- specified. For a 'Maybe' type parameter, we allow that it is not |
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-- present (via 'Utils.maybeFromObj'). Otherwise, if there is a |
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-- default value, we allow the parameter to be abset, and finally if |
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-- there is no default value, we require its presence. |
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loadField :: OpParam -> Q (Name, Stmt) |
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loadField (fname, qt, qdefa) = do |
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let fvar = mkName fname |
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t <- qt |
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defa <- qdefa |
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-- these are used in all patterns below |
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let objvar = varNameE "o" |
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objfield = stringE fname |
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bexp <- if isOptional t |
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then [| $((varNameE "maybeFromObj")) $objvar $objfield |] |
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else case defa of |
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AppE (ConE dt) defval | dt == 'Just -> |
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-- but has a default value |
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[| $(varNameE "fromObjWithDefault") |
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$objvar $objfield $(return defval) |] |
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ConE dt | dt == 'Nothing -> |
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[| $(varNameE "fromObj") $objvar $objfield |] |
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s -> fail $ "Invalid default value " ++ show s ++ |
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", expecting either 'Nothing' or a 'Just defval'" |
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return (fvar, BindS (VarP fvar) bexp) |
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|
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loadConstructor :: String -> [OpParam] -> Q Exp |
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loadConstructor sname fields = do |
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let name = mkName sname |
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fbinds <- mapM loadField fields |
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let (fnames, fstmts) = unzip fbinds |
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let cval = foldl (\accu fn -> AppE accu (VarE fn)) (ConE name) fnames |
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fstmts' = fstmts ++ [NoBindS (AppE (VarE 'return) cval)] |
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return $ DoE fstmts' |
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|
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genLoadOpCode :: [(String, [OpParam])] -> Q (Dec, Dec) |
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genLoadOpCode opdefs = do |
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let fname = mkName "loadOpCode" |
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arg1 = mkName "v" |
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objname = mkName "o" |
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opid = mkName "op_id" |
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st1 <- bindS (varP objname) [| liftM JSON.fromJSObject |
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(JSON.readJSON $(varE arg1)) |] |
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st2 <- bindS (varP opid) [| $(varNameE "fromObj") |
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$(varE objname) $(stringE "OP_ID") |] |
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-- the match results (per-constructor blocks) |
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mexps <- mapM (uncurry loadConstructor) opdefs |
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fails <- [| fail $ "Unknown opcode " ++ $(varE opid) |] |
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let mpats = map (\(me, c) -> |
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let mp = LitP . StringL . deCamelCase . fst $ c |
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in Match mp (NormalB me) [] |
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) $ zip mexps opdefs |
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defmatch = Match WildP (NormalB fails) [] |
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cst = NoBindS $ CaseE (VarE opid) $ mpats++[defmatch] |
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body = DoE [st1, st2, cst] |
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sigt <- [t| JSON.JSValue -> JSON.Result $(conT (mkName "OpCode")) |] |
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return $ (SigD fname sigt, FunD fname [Clause [VarP arg1] (NormalB body) []]) |
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|
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-- | No default type. |
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noDefault :: Q Exp |
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noDefault = conE 'Nothing |