From 78fc982247d2f5a02131c61f8e1279268dd93033 Mon Sep 17 00:00:00 2001
From: Camil Staps
Date: Tue, 14 Nov 2017 12:04:50 +0100
Subject: Start & cleanup assignment 8

---
 assignment-8/skeleton8.icl | 63 +++++++++++++++++++++++++++++++++++++---------
 1 file changed, 51 insertions(+), 12 deletions(-)

diff --git a/assignment-8/skeleton8.icl b/assignment-8/skeleton8.icl
index 0c68ac9..3e81cce 100644
--- a/assignment-8/skeleton8.icl
+++ b/assignment-8/skeleton8.icl
@@ -5,6 +5,21 @@ module skeleton8
  * Pieter Koopman, pieter@cs.ru.nl
  */
 
+import StdList
+import StdString
+
+import Control.Applicative
+import Control.Monad
+from Control.Monad.State import :: StateT(StateT),
+	instance Functor (StateT s m), instance Applicative (StateT s m), instance Monad (StateT s m),
+	gets, modify
+import Data.Error
+from Data.Func import $
+import Data.Functor
+import qualified Data.Map as Map
+import Data.Maybe
+from Text import <+
+
 from iTasks import class iTask, class toPrompt, class Publishable, instance Publishable Task,
 	instance toPrompt String, instance Functor Task,
 	class TApplicative, instance TApplicative Task,
@@ -14,12 +29,13 @@ from iTasks import class iTask, class toPrompt, class Publishable, instance Publ
 	-||-, -||, ||-, >>*, always, hasValue, updateInformation, viewInformation, startEngine
 import qualified iTasks
 import qualified iTasks.WF.Combinators.Overloaded as WF
-import Data.Functor, Control.Applicative, Control.Monad
-import Data.Tuple, StdClass, StdList, StdMaybe, StdString
-import StdGeneric, StdBool
-from StdFunc import o
-import qualified Data.List as List
-import qualified Data.Map as Map
+
+(>>>=)     :== 'iTasks'.tbind
+(>>>|) a b :== 'iTasks'.tbind a (\_ -> b)
+treturn    :== 'iTasks'.return
+ActionOk   :== 'iTasks'.ActionOk
+ActionQuit :== 'iTasks'.ActionQuit
+ActionNew  :== 'iTasks'.ActionNew
 
 :: Expression
 	= New      [Int]
@@ -52,16 +68,39 @@ import qualified Data.Map as Map
 
 // === State
 
+:: Val
+	= VElem Int
+	| VSet  [Int]
+
+:: State :== 'Map'.Map Ident Val
+
+:: Sem a :== StateT State (MaybeError String) a
+// Or define :: Sem a = Sem (s -> MaybeErrorString (a,s)) and copy the relevant
+// instances from Control.Monad.State
+
+store :: Ident Val -> Sem Val
+store i v = modify ('Map'.put i v) $> v
+
+read :: Ident -> Sem Val
+read i = gets ('Map'.get i) >>= \v -> case v of
+	Nothing -> fail $ "unknown variable '" <+ i <+ "'"
+	Just v  -> pure v
+
+fail :: String -> Sem a
+fail e = StateT \_ -> Error e
+
+eval :: Expression -> Sem Val
+eval (New xs) = pure $ VSet  xs
+eval (Elem x) = pure $ VElem x
+eval (Variable i) = read i
+eval (Size s)     = eval s >>= \xs -> case xs of
+	VSet xs -> pure $ VElem $ length xs
+	_       -> fail "Size :: Set -> Elem applied to Elem"
+//eval (a +. b) TODO
 
 // === semantics
 
 
 // === simulation
-(>>>=)     :== 'iTasks'.tbind
-(>>>|) a b :== 'iTasks'.tbind a (\_ -> b)
-treturn    :== 'iTasks'.return
-ActionOk   :== 'iTasks'.ActionOk
-ActionQuit :== 'iTasks'.ActionQuit
-ActionNew  :== 'iTasks'.ActionNew
 
 Start = ()
-- 
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