CIS 5520: Advanced Programming
Note: this is the stubbed version of module LSyntax. Try to figure out
how to fill in all parts of this file marked
undefined.
CIS 5520 students should be able to access this code through
github. Eventually, the
completed version will be available.
In class exercise: LSyntax
This file defines the abstract syntax for a simple imperative programming (L) language extended with exceptions.
It is meant to go with the in-class exercise on monad transformers (TransExercise)[TransExercise.hs].
> module LSyntax whereSyntax
> type Var = String -- only global variables, no tables> newtype Block =
> Block [ Statement ] -- s1 ... sn
> deriving (Eq, Show)> instance Semigroup Block where
> (<>) :: Block -> Block -> Block
> Block s1 <> Block s2 = Block (s1 <> s2)> instance Monoid Block where
> mempty :: Block
> mempty = Block []> data Statement =
> Assign Var Expression -- x = e
> | If Expression Block Block -- if e then s1 else s2
> | While Expression Block -- while e s
> | Try Block Var Block -- try s1 handle x in s2
> | Throw Expression -- throw e
> deriving (Eq, Show)> data Expression =
> Var Var -- x
> | Val Value -- v
> | Op2 Expression Bop Expression -- e1 op e2
> deriving (Eq, Show)> data Bop =
> Plus -- `+` :: Int -> Int -> Int
> | Minus -- `-` :: Int -> Int -> Int
> | Times -- `*` :: Int -> Int -> Int
> | Divide -- `//` :: Int -> Int -> Int
> deriving (Eq, Show, Enum)> data Value =
> IntVal Int -- literal ints
> | NilVal -- `nil`
> deriving (Eq, Show)