Added tests. Small improvements to README

Author: lucasimi

README.md

@@ -1,6 +1,6 @@
 # Minilisp
 
-Minilisp is a very simple Lisp-like interactive environment based on the well-known paper by John McCarty (http://www-formal.stanford.edu/jmc/recursive.pdf). Minilisp is written in Haskell and is an example of how intepreter/compiler design can be easy using functional programming.
+Minilisp is a Lisp-like interactive environment for on-the-fly function prototyping. Based on the well-known paper by John McCarthy (http://www-formal.stanford.edu/jmc/recursive.pdf) Minilisp aims to be minimal and self-contained but expandable.
 
 # Features
 

package.yaml

@@ -24,11 +24,12 @@ dependencies:
 - haskeline >= 0.7 && < 0.8
 - hspec >= 2.6.1
 - containers >= 0.6.0.1
+- QuickCheck >= 2.12.6.1
 
 library:
   source-dirs:
     - src
-    
+
 executables:
   minilisp-exe:
     main:                Main.hs

src/Interpreter.hs

@@ -268,6 +268,36 @@ evalGreater env ctx x y = do
       False -> return (env, ctx, F)
     _ -> runtimeError "Type mismatch"
 
+evalOr :: Env -> Ctx -> SExpr -> SExpr -> Effect (Env, Ctx, SExpr)
+evalOr env ctx x y = do
+  (_, _, x') <- eval env ctx x
+  (_, _, y') <- eval env ctx y
+  case (x', y') of
+    (T, T) -> return (env, ctx, T)
+    (F, T) -> return (env, ctx, T)
+    (T, F) -> return (env, ctx, T)
+    (F, F) -> return (env, ctx, F)
+    _ -> runtimeError "Non boolean values"
+
+evalAnd :: Env -> Ctx -> SExpr -> SExpr -> Effect (Env, Ctx, SExpr)
+evalAnd env ctx x y = do
+  (_, _, x') <- eval env ctx x
+  (_, _, y') <- eval env ctx y
+  case (x', y') of
+    (T, T) -> return (env, ctx, T)
+    (T, F) -> return (env, ctx, F)
+    (F, T) -> return (env, ctx, F)
+    (F, F) -> return (env, ctx, F)
+    _ -> runtimeError "Non boolean values"
+
+evalNot :: Env -> Ctx -> SExpr -> Effect (Env, Ctx, SExpr)
+evalNot env ctx x = do
+  (_, _, x') <- eval env ctx x
+  case x' of
+    T -> return (env, ctx, F)
+    F -> return (env, ctx, T)
+    _ -> runtimeError "Non boolean value"
+
 -- evaluation function, the core of the lisp interpreter
 eval :: Env -> Ctx -> SExpr -> Effect (Env, Ctx, SExpr)
 -- evaluation of atomic values (self-evaluation)
@@ -303,6 +333,9 @@ eval env ctx (DIV x y) = evalDiv env ctx x y
 eval env ctx (MOD x y) = evalMod env ctx x y
 eval env ctx (LESS x y) = evalLess env ctx x y
 eval env ctx (GREATER x y) = evalGreater env ctx x y
+eval env ctx (AND x y) = evalAnd env ctx x y
+eval env ctx (OR x y) = evalOr env ctx x y
+eval env ctx (NOT x) = evalNot env ctx x
 -- evaluation of non built-in functions
 eval env ctx (Pair f x) = do
   (env', ctx', f') <- eval env ctx f

src/Parser.hs

@@ -85,6 +85,9 @@ compile (Node (Leaf (SymbType "/")) (Node x (Node y Empty))) = DIV (compile x) (
 compile (Node (Leaf (SymbType "%")) (Node x (Node y Empty))) = MOD (compile x) (compile y)
 compile (Node (Leaf (SymbType "<")) (Node x (Node y Empty))) = LESS (compile x) (compile y)
 compile (Node (Leaf (SymbType ">")) (Node x (Node y Empty))) = GREATER (compile x) (compile y)
+compile (Node (Leaf (SymbType "or")) (Node x (Node y Empty))) = OR (compile x) (compile y)
+compile (Node (Leaf (SymbType "and")) (Node x (Node y Empty))) = AND (compile x) (compile y)
+compile (Node (Leaf (SymbType "not")) (Node x Empty)) = NOT (compile x)
 
 compile (Node x y) = Pair (compile x) (compile y)
 

src/SExpr.hs

@@ -8,8 +8,8 @@ data SExpr = Nil
            | Double Double
            | String String
            | Symb String
-           | Pair SExpr SExpr
            | Lambda [SExpr] SExpr
+           | Pair SExpr SExpr
            | CAR SExpr
            | CDR SExpr
            | CONS SExpr SExpr
@@ -28,6 +28,9 @@ data SExpr = Nil
            | MOD SExpr SExpr
            | LESS SExpr SExpr
            | GREATER SExpr SExpr
+           | OR SExpr SExpr
+           | AND SExpr SExpr
+           | NOT SExpr
            deriving Eq
 
 instance Show SExpr where