# File eval mode now relies on main function

To encourage organizing code in a way that helps in understanding, I
have implemented the common idiom of requiring a `main` function. In
tricu and other functional languages, it is usually placed near the top
of the module. The evaluator gracefully handles the situation of passing
multiple files where the intermediary "library" files do not have main functions.

src/Main.hs

@@ -1,6 +1,6 @@
 module Main where
 
-import Eval                   (evalTricu, result)
+import Eval                   (evalTricu, mainResult, result)
 import FileEval
 import Parser                 (parseTricu)
 import REPL
@@ -16,7 +16,7 @@ import qualified Data.Map as Map
 data TricuArgs
   = Repl
   | Evaluate { file :: [FilePath], form :: EvaluatedForm }
-  | Decode { file :: [FilePath] }
+  | TDecode { file :: [FilePath] }
   deriving (Show, Data, Typeable)
 
 replMode :: TricuArgs
@@ -31,7 +31,7 @@ evaluateMode = Evaluate
       \ Defaults to stdin."
       &= name "f" &= typ "FILE"
     , form = TreeCalculus &= typ "FORM"
-      &= help "Optional output form: (tree|fsl|ast|ternary|ascii).\n \
+      &= help "Optional output form: (tree|fsl|ast|ternary|ascii|decode).\n \
       \ Defaults to tricu-compatible `t` tree form."
       &= name "t"
   }
@@ -40,7 +40,7 @@ evaluateMode = Evaluate
   &= name "eval"
 
 decodeMode :: TricuArgs
-decodeMode = Decode
+decodeMode = TDecode
   { file = def
     &= help "Optional input file path to attempt decoding.\n \
     \ Defaults to stdin."
@@ -70,10 +70,10 @@ main = do
         (filePath:restFilePaths) -> do
             initialEnv <- evaluateFile filePath
             finalEnv <- foldM evaluateFileWithContext initialEnv restFilePaths
-            pure $ result finalEnv
+            pure $ mainResult finalEnv
       let fRes = formatResult form result
       putStr fRes
-    Decode { file = filePaths } -> do
+    TDecode { file = filePaths } -> do
       value <- case filePaths of
         [] -> getContents
         (filePath:_) -> readFile filePath