You have fixed the type of list by move RAX RAX. Now it has type Instruction SNDREG SNDREG

Make your Instruction a GADT and require that MOV should have appropriate constraints:

{-# LANGUAGE DatatypeContexts, GADTs #-}

data SREG = RIP
data DREG = RBX
data SNDREG = RAX

data Instruction where
MOV :: (Source s, Destination d) => s -> d -> Instruction

class Source a
class Destination a

instance Source SREG
instance Source SNDREG

instance Destination DREG
instance Destination SNDREG

move :: (Source s, Destination d) => s -> d -> Instruction
move s d = MOV s d

hello = [move RAX RAX, move RAX RAX]

hello2 = [move RAX RAX, move RAX RBX] -- this is still not allowed.

2013/4/1 C K Kashyap <ckkashyap@gmail.com>

Hi Cafe,
I am trying to embed x86 assembly in Haskell. I'd like the EDSL to not allow invalid movements into registers - for example, should not allow moving into RIP. I was not able to get it to work. I ended up using DataTypeContexts - which is considered misfeature anyway. I was wondering if I could get some suggestions.

{-# LANGUAGE DatatypeContexts #-}

data SREG = RIP
data DREG = RBX
data SNDREG = RAX

data (Source s, Destination d) => Instruction s d = MOV s d

class Source a
class Destination a

instance Source SREG
instance Source SNDREG

instance Destination DREG
instance Destination SNDREG

move :: (Source s, Destination d) => s -> d -> Instruction s d
move s d = MOV s d

hello = [move RAX RAX, move RAX RAX]

hello = [move RAX RAX, move RAX RBX] -- this is still not allowed.

Regards,
Kashyap

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