Added programming language fundamentals code. More to come.

OSU Coursework/CS 381 - Programming Language Fundamentals/Homework 4/StackRank.Turkingk.hs

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+module StackTypes where
+
+
+--
+-- * Part 1: A Rank-Based Type System for the Stack Language
+--
+-- ** The abstract syntax
+--
+type Prog = [Cmd]
+
+data Cmd = Push Int
+         | Pop Int
+         | Add
+         | Mul
+         | Dup
+         | Inc
+         | Swap
+         deriving(Eq,Show)
+
+type Stack = [Int]
+
+type Rank = Int
+
+-- NOTES:      (popsnum on stack,pushes on stack)
+type CmdRank = (Int,Int)
+
+
+-- ** The semantic function that yields the semantics of a program
+--
+prog :: Prog -> Stack -> Maybe Stack
+prog []     s = Just s
+prog (c:cs) s = cmd c s >>= prog cs
+
+
+-- ** The semantics function that yields the semantics of a command
+--
+cmd :: Cmd -> Stack -> Maybe Stack
+cmd (Push n) s       = Just (n:s)
+cmd (Pop  k) s       = Just (drop k s)
+cmd Add      (n:k:s) = Just (n + k:s)
+cmd Mul      (n:k:s) = Just (n * k:s)
+cmd Dup      (n:s)   = Just (n:n:s)
+cmd Inc      (n:s)   = Just (n + 1:s)
+cmd Swap     (n:k:s) = Just (k:n:s)
+cmd _        _       = Nothing
+
+
+
+-- | 1. Define the function rankC that maps each stack operation to its rank
+--
+rankC :: Cmd -> CmdRank
+rankC (Push _) = (0,1)
+rankC (Pop x)  = (x,0)
+rankC (Add)    = (2,1)
+rankC (Mul)    = (2,1)
+rankC (Dup)    = (1,2)
+rankC (Inc)    = (1,1)
+rankC (Swap)   = (2,2)
+
+-- | 2. Define the auxiliary function rankP that computes the rank of programs
+--
+rankP :: Prog -> Rank -> Maybe Rank
+rankP [] x = Just x
+rankP cmds x = rank cmds x
+
+rank :: Prog -> Rank -> Maybe Rank
+rank [] x = Just x
+rank (x:xs) r = let (popsnum,pushsnum) = rankC x in
+                    if (popsnum < r) then rank xs (r - popsnum + pushsnum)
+                    else Nothing
+
+rankPMapper :: Prog -> [CmdRank]
+rankPMapper [] = []
+rankPMapper cmds = map rankC cmds
+
+-- | 3. Define the semantic function semStatTC for evaluating stack programs
+--
+semStatTC :: Prog -> Stack -> Maybe Stack
+semStatTC prg stk = if (rankP prg (length stk)) == Nothing then Nothing
+                    else prog prg stk
+
+
+-- | EXTRA CREDIT
+--
+-- prog' = undefined
+
+
+
+-- * Part 2: Runtime Stack
+--
+
+
+
+-- * Part 3: Static and Dynamic Scope
+--