-----------------------------------------------------------------------------
module Debug.Trace (
- -- * Tracing
- putTraceMsg, -- :: String -> IO ()
- trace -- :: String -> a -> a
+ -- * Tracing
+ putTraceMsg, -- :: String -> IO ()
+ trace, -- :: String -> a -> a
+ traceShow
) where
import Prelude
withCString msg $ \cmsg ->
debugBelch cfmt cmsg
-foreign import ccall unsafe debugBelch :: CString -> CString -> IO ()
+-- don't use debugBelch() directly, because we cannot call varargs functions
+-- using the FFI.
+foreign import ccall unsafe "HsBase.h debugBelch2"
+ debugBelch :: CString -> CString -> IO ()
#endif
{-# NOINLINE trace #-}
trace string expr = unsafePerformIO $ do
putTraceMsg string
return expr
+
+{-|
+Like 'trace', but uses 'show' on the argument to convert it to a 'String'.
+
+> traceShow = trace . show
+-}
+traceShow :: (Show a) => a -> b -> b
+traceShow = trace . show