base-4.2.0.0: Basic librariesSource codeContentsIndex
Debug.Trace
Portabilityportable
Stabilityprovisional
Maintainerlibraries@haskell.org
Contents
Tracing
Description
The trace function.
Synopsis
putTraceMsg :: String -> IO ()
trace :: String -> a -> a
traceShow :: Show a => a -> b -> b
Tracing
putTraceMsg :: String -> IO ()Source
putTraceMsg function outputs the trace message from IO monad. Usually the output stream is System.IO.stderr but if the function is called from Windows GUI application then the output will be directed to the Windows debug console.
trace :: String -> a -> aSource
When called, trace outputs the string in its first argument, before returning the second argument as its result. The trace function is not referentially transparent, and should only be used for debugging, or for monitoring execution. Some implementations of trace may decorate the string that's output to indicate that you're tracing. The function is implemented on top of putTraceMsg.
traceShow :: Show a => a -> b -> bSource

Like trace, but uses show on the argument to convert it to a String. 

 traceShow = trace . show
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