Immutable definitions and documentation updates

2025-01-24 16:14:33 -06:00
parent 88b1c71695
commit 3175132eec
6 changed files with 137 additions and 32 deletions
--- a/src/Eval.hs
+++ b/src/Eval.hs
@ -11,8 +11,13 @@ import qualified Data.Set as Set
 evalSingle :: Env -> TricuAST -> Env
 evalSingle env term
  | SFunc name [] body <- term =
-      let res = evalAST env body
-      in Map.insert "__result" res (Map.insert name res env)
+      if
+        | Map.member name env -> 
+            errorWithoutStackTrace $ 
+              "Error: Identifier '" ++ name ++ "' is already defined."
+        | otherwise -> 
+            let res = evalAST env body
+            in Map.insert "__result" res (Map.insert name res env)
  | SApp func arg <- term =
      let res = apply (evalAST env func) (evalAST env arg)
      in Map.insert "__result" res env