jacobstanley/trace.hs

Created August 14, 2019 10:05

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jacobstanley created this gist Aug 14, 2019.

trace.hs

-Original file line number
+Diff line change
@@ -0,0 +1,11 @@
+    import qualified System.Console.Concurrent as Concurrent
+    trace :: [Char] -> a -> a
+    trace string expr =
+      unsafePerformIO $ do
+        traceIO string
+        return expr
+    traceIO :: [Char] -> IO ()
+    traceIO string = do
+      Concurrent.errorConcurrent (string <> "\n")