reorganized and started working on unit tests

dependent-lambda.cabal

@@ -1,22 +1,6 @@
 cabal-version:      3.0
--- The cabal-version field refers to the version of the .cabal specification,
--- and can be different from the cabal-install (the tool) version and the
--- Cabal (the library) version you are using. As such, the Cabal (the library)
--- version used must be equal or greater than the version stated in this field.
--- Starting from the specification version 2.2, the cabal-version field must be
--- the first thing in the cabal file.
-
--- Initial package description 'dependent-lambda' generated by
--- 'cabal init'. For further documentation, see:
---   http://haskell.org/cabal/users-guide/
---
--- The name of the package.
 name:               dependent-lambda
 
--- The package version.
--- See the Haskell package versioning policy (PVP) for standards
--- guiding when and how versions should be incremented.
--- https://pvp.haskell.org
 -- PVP summary:     +-+------- breaking API changes
 --                  | | +----- non-breaking API additions
 --                  | | | +--- code changes with no API change
@@ -28,56 +12,54 @@ version:            0.1.0.0
 -- A longer description of the package.
 -- description:
 
--- The license under which the package is released.
 license:            GPL-3.0-or-later
-
--- The file containing the license text.
 license-file:       LICENSE
 
--- The package author(s).
 author:             William Ball
-
--- An email address to which users can send suggestions, bug reports, and patches.
 maintainer:         williampi103@gmail.com
 
--- A copyright notice.
--- copyright:
 category:           Math
 build-type:         Simple
 
--- Extra doc files to be distributed with the package, such as a CHANGELOG or a README.
 extra-doc-files:    CHANGELOG.md
+                  , README.md
 
 -- Extra source files to be distributed with the package, such as examples, or a tutorial module.
 -- extra-source-files:
 
-common warnings
-    ghc-options: -Wall
-
-executable dependent-lambda
-    -- Import common warning flags.
-    import:           warnings
-
-    -- .hs or .lhs file containing the Main module.
-    main-is:          Main.hs
-
-    -- Modules included in this executable, other than Main.
-    other-modules:    Expr
-                      Check
+library dependent-lambda-lib
+    exposed-modules:  Check
                       Parser
+                      Expr
 
-    -- LANGUAGE extensions used by modules in this package.
-    -- other-extensions:
-
-    -- Other library packages from which modules are imported.
+    hs-source-dirs:   lib
     build-depends:    base ^>=4.19.1.0
                     , megaparsec
                     , text
                     , parser-combinators
                     , mtl
-
-    -- Directories containing source files.
-    hs-source-dirs:   app
-
-    -- Base language which the package is written in.
+    default-language: Haskell2010
+
+common warnings
+    ghc-options: -Wall
+
+executable dependent-lambda
+    import:           warnings
+    main-is:          Main.hs
+
+    build-depends:    base ^>=4.19.1.0
+                    , dependent-lambda-lib
+    hs-source-dirs:   app
+    default-language: Haskell2010
+
+test-suite tests
+    type:             exitcode-stdio-1.0
+    main-is:          Tests.hs
+    other-modules:    ExprTests
+                    , ParserTests
+                    , CheckTests
+    build-depends:    base ^>=4.19.1.0
+                    , HUnit
+                    , dependent-lambda-lib
+    hs-source-dirs:   tests
     default-language: Haskell2010

lib/Expr.hs

@@ -118,7 +118,8 @@ incIndices = shiftIndices 1 0
 subst :: Integer -> Expr -> Expr -> Expr
 subst k s (Var n x)
     | k == n = s
-    | otherwise = Var (n - 1) x
+    | n > k = Var (n - 1) x
+    | otherwise = Var n x
 subst _ _ Star = Star
 subst _ _ Square = Square
 subst k s (App m n) = App (subst k s m) (subst k s n)

tests/CheckTests.hs

@@ -0,0 +1 @@
+module CheckTests where

tests/ExprTests.hs

@@ -0,0 +1,52 @@
+module ExprTests where
+
+import Expr
+import Test.HUnit
+
+inner :: Expr
+inner = Abs "x" (Var 0 "A") $ Var 2 "f" <.> Var 0 "x"
+
+e1 :: Expr
+e1 = Abs "A" Star inner
+
+fFree :: Test
+fFree = TestCase $ assertBool "f free" $ occursFree 0 e1
+
+incE1 :: Test
+incE1 =
+    TestCase $
+        assertEqual
+            "incIndices e1"
+            ( Abs "A" Star $
+                Abs "x" (Var 0 "A") $
+                    Var 3 "f" <.> Var 0 "x"
+            )
+            (incIndices e1)
+
+after :: Expr
+after = Abs "x" (Var 2 "B") $ Var 1 "f" <.> Var 0 "x"
+
+substE1 :: Test
+substE1 =
+    TestCase $
+        assertEqual
+            "e1[A := B]"
+            after
+            (subst 0 (Var 2 "B") inner)
+
+betaNFe1 :: Test
+betaNFe1 =
+    TestCase $
+        assertEqual
+            "e1 B"
+            after
+            (betaNF $ e1 <.> Var 2 "B")
+
+tests :: Test
+tests =
+    TestList
+        [ TestLabel "fFree" fFree
+        , TestLabel "incE1" incE1
+        , TestLabel "substE1" substE1
+        , TestLabel "betaNFe1" betaNFe1
+        ]

tests/ParserTests.hs

@@ -0,0 +1 @@
+module ParserTests where

tests/Tests.hs

@@ -0,0 +1,13 @@
+module Main where
+
+import qualified ExprTests as E
+import qualified System.Exit as Exit
+import Test.HUnit
+
+tests :: Test
+tests = TestList [TestLabel "ExprTests" E.tests]
+
+main :: IO ()
+main = do
+    result <- runTestTT tests
+    if failures result > 0 then Exit.exitFailure else Exit.exitSuccess