base-3.0.2.0: Basic libraries Source code Contents Index

Debug.Trace Portability portable Stability provisional Maintainer libraries@haskell.org

Contents Tracing

Description

The trace function.

Synopsis

putTraceMsg :: String -> IO () trace :: String -> a -> a

Tracing

putTraceMsg :: String -> IO () Source

putTraceMsg function outputs the trace message from IO monad. Usually the output stream is 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 -> a Source

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.

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