Add some concept docs

8 files changed, 80 insertions, 6 deletions

diff --git a/app/Main.hs b/app/Main.hs
index 113a3ba..0fe5551 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -15,6 +15,8 @@ parseArgs config args =
             config { configVerboseMode = True } rest
         ("-h":rest) -> parseArgs
             config { configShowHelp = True } rest
+        ("-e":rest) -> parseArgs
+            config { configPrintEvaled = True } rest
         _ -> config
 
 repl :: Config -> Env -> InputT IO ()
@@ -39,7 +41,8 @@ main = do
     let initialConfig = Config {
         configScriptFileName = Nothing,
         configVerboseMode = False,
-        configShowHelp = False
+        configShowHelp = False,
+        configPrintEvaled = False
     }
 
     let config = parseArgs initialConfig args
@@ -48,6 +51,7 @@ main = do
         putStrLn $ "Usage: " ++ progName ++ "                 # to open REPL"
         putStrLn $ "       " ++ progName ++ " -i scriptFile   # to run script file"
         putStrLn $ "       " ++ progName ++ " -h              # to show this help"
+        putStrLn $ "       " ++ progName ++ " -e              # to automatically print results of evaluated expressions to stdout"
     else do
         when (configVerboseMode config) $ do
             putStrLn $ "configScriptFileName:\t" ++ (show $ configScriptFileName config)
diff --git a/examples/algebraic-types-concept.lisp b/examples/algebraic-types-concept.lisp
new file mode 100644
index 0000000..315a693
--- /dev/null
+++ b/examples/algebraic-types-concept.lisp
@@ -0,0 +1,19 @@
+(let just (\[a]
+    ["maybe" "just" a]))
+(let nothing (\[]
+    ["maybe" "nothing"]))
+
+(let at (\[n seq]
+    (match seq
+        [] (nothing)
+        (match n
+            0 (head seq)
+            (at (- n 1) (tail seq))))))
+
+(let from-just (at 2))
+(let kind (at 1))
+
+(let m (just 10))
+(match (kind m)
+    "just" (from-just m)
+    "nothing" "nothing")
diff --git a/examples/effects-concept.lisp b/examples/effects-concept.lisp
new file mode 100644
index 0000000..efca43e
--- /dev/null
+++ b/examples/effects-concept.lisp
@@ -0,0 +1,19 @@
+; FUNCTIONS
+
+(let prompt-input (\[]
+    (let p "> ")
+    (do get-user-input "prompted" p)))
+
+; SIGNAL HANDLERS
+
+(on user-input (\[msg s]
+    (match msg
+        "prompted" (batch [
+            (do print-line (fmt "You entered: %%" [s]))
+            (prompt-input)])
+        (batch [
+            (do fatal-error (fmt "error: unknown signal %%" [msg]))]))))
+
+;; ENTRYPOINT
+
+(prompt-input)
diff --git a/src/Builtins.hs b/src/Builtins.hs
index a4676b8..2eedbed 100644
--- a/src/Builtins.hs
+++ b/src/Builtins.hs
@@ -13,7 +13,9 @@ builtinEnv = M.fromList [
     ("/", builtinDivide2),
     ("head", builtinHead),
     ("tail", builtinTail),
-    ("prepend", builtinPrepend)
+    ("prepend", builtinPrepend),
+    ("print!", builtinPrint),
+    ("string-concat", builtinStringConcat2)
     ]
 
 -- maybe make a builtinBinaryFunction?
@@ -93,3 +95,21 @@ builtinPrepend =
                     return $ ASTVector $ ast1 : vec
             return $ ASTFunction $ inner
      in ASTFunction outer
+
+builtinPrint :: AST
+builtinPrint =
+    let outer _ ast =
+         do (ASTString str) <- assertIsASTString ast
+            liftIO $ putStr $ str
+            return ASTUnit
+     in ASTFunction outer
+
+builtinStringConcat2 :: AST
+builtinStringConcat2 =
+    let outer _ ast1 = do
+            (ASTString str1) <- assertIsASTString ast1
+            let inner _ ast2 = do
+                    (ASTString str2) <- assertIsASTString ast2
+                    return $ ASTString $ str1 ++ str2
+            return $ ASTFunction $ inner
+     in ASTFunction outer
diff --git a/src/Lib.hs b/src/Lib.hs
index 00d9f37..a2c65c6 100644
--- a/src/Lib.hs
+++ b/src/Lib.hs
@@ -23,11 +23,16 @@ runInlineScript env src = do
     config <- ask
     when (configVerboseMode config) $ liftIO $ putStrLn $ "tokenized:\t\t" ++ show tokenized
     parsed <- parse tokenized
+
     when (configVerboseMode config) $ do
         let output = "parsed:\t\t\t" ++ (map show parsed $> L.intercalate "\n\t\t\t")
         liftIO $ putStrLn output
+
     (newEnv, evaluated) <- foldEvaluate env parsed
-    liftIO $ mapM_ putStrLn (map show evaluated)
+
+    when (configPrintEvaled config) $ do
+        liftIO $ mapM_ putStrLn (map show evaluated)
+
     return (newEnv, evaluated)
         where
             foldEvaluate :: Env -> [AST] -> LContext (Env, [AST])
diff --git a/src/Utils.hs b/src/Utils.hs
index 76f1524..e0695c3 100644
--- a/src/Utils.hs
+++ b/src/Utils.hs
@@ -13,7 +13,8 @@ newtype LException = LException String
 data Config = Config {
     configScriptFileName :: Maybe String,
     configVerboseMode :: Bool,
-    configShowHelp :: Bool
+    configShowHelp :: Bool,
+    configPrintEvaled :: Bool
 }
 
 type LContext a = ReaderT Config (ExceptT LException IO) a
@@ -95,6 +96,11 @@ assertIsASTVector ast = case ast of
     (ASTVector _) -> return ast
     _ -> throwL $ show ast ++ " is not a vector"
 
+assertIsASTString :: AST -> LContext AST
+assertIsASTString ast = case ast of
+    (ASTString _) -> return ast
+    _ -> throwL $ show ast ++ " is not a string"
+
 assertIsASTFunctionCall :: AST -> LContext AST
 assertIsASTFunctionCall ast = case ast of
     (ASTFunctionCall _) -> return ast
diff --git a/test/TestUtils.hs b/test/TestUtils.hs
index ad31c78..e51d97b 100644
--- a/test/TestUtils.hs
+++ b/test/TestUtils.hs
@@ -7,7 +7,8 @@ testConfig :: Config
 testConfig = Config {
     configScriptFileName = Nothing,
     configVerboseMode = False,
-    configShowHelp = False
+    configShowHelp = False,
+    configPrintEvaled = False
 }
 
 testRunL :: LContext a -> IO (Either LException a)
diff --git a/todo.md b/todo.md
index baebacf..d4dd292 100644
--- a/todo.md
+++ b/todo.md
@@ -7,8 +7,8 @@ In order of priority
 - Add builtins to convert from int to double and vice versa
 - Add builtin to convert to string
 - Add builtins to compare numbers (eq?, lt?)
-- Add flag to control whether computed values are automatically printed or not
 - Add import function with support for qualified imports
 - Come up with a name for the language
 - Add auto import for standard library (std)
 - Add flag to disable auto import of standard library
+- Add effects system (see `examples/effects-concept.lisp`)