gistfile1.hs

-- An Addr is really 14 bits, but this should be close enough
type Addr = Word16

-- The status register
type StatusR = On | Off deriving (Show, Eq)

type Imm =   LTZ
           | LEZ
           | EQZ
           | GEZ
           | GTZ deriving (Show, Eq, Ord, Enum)



data DOper =   Add
            | Sub
            | Mult -- etc.

data DType = DOper Addr Addr

data SType = SOper (Maybe Imm) Addr

-- The program counter
type ProgramCounter = Addr

-- The instruction set is immutable
type Instructions = IArray Addr Word32

-- Memory is mutable
type Memory = IOArray Addr Word64

data World = World ProgramCounter StatusR Instructions Memory

-- Stepping through a single instruction is a function like World -> IO
-- World. The new world has an incremented ProgramCounter, and shares the same
-- reference to an Instruction array and Memory array. Since the memory array is
-- mutable, the old world shouldn't be used anymore (since its memory contents
-- will reflect the new state of the world).