🚂 Equality and power

a3/a3-handout/src/APL/Parser.hs

@@ -96,12 +96,26 @@ pLExp =
       pFExp
     ]
 
-pExp1 :: Parser Exp
-pExp1 = pLExp >>= chain
+pPExp :: Parser Exp
+pPExp = pLExp >>= chain
   where
     chain x =
       choice
-        [ do
+        [
+          do
+            lString "**"
+            y <- pPExp
+            chain $ Pow x y,
+          pure x
+        ]
+
+pExp1 :: Parser Exp
+pExp1 = pPExp >>= chain
+  where
+    chain x =
+      choice
+        [
+          do
             lString "*"
             y <- pLExp
             chain $ Mul x y,
@@ -125,6 +139,10 @@ pExp0 = pExp1 >>= chain
             lString "-"
             y <- pExp1
             chain $ Sub x y,
+          do
+            lString "=="
+            y <- pExp1
+            chain $ Eql x y,
           pure x
         ]
 

a3/a3-handout/src/APL/Parser_Tests.hs

@@ -70,5 +70,17 @@ tests =
         [ parserTest "x y" $ Apply (Var "x") (Var "y"),
           parserTest "x y z" $ Apply (Apply (Var "x") (Var "y")) (Var "z"),
           parserTest "x (y z)" $ Apply (Var "x") (Apply (Var "y") (Var "z"))
+        ],
+      testGroup
+        "Eql"
+        [ parserTest "x == y" $ Eql (Var "x") (Var "y"),
+          parserTest "x == y == z" $ Eql (Eql (Var "x") (Var "y")) (Var "z"),
+          parserTest "x + y == z * x" $ Eql (Add (Var "x") (Var "y")) (Mul (Var "z") (Var "x"))
+        ],
+      testGroup
+        "Eql"
+        [ parserTest "x ** y" $ Pow (Var "x") (Var "y"),
+          parserTest "x ** y ** z" $ Pow (Var "x") (Pow (Var "y") (Var "z")),
+          parserTest "x + y ** z * x" $  Add (Var "x") (Mul (Pow (Var "y") (Var "z")) (Var "x"))
         ]
     ]