diff options
Diffstat (limited to 'libraries/base/Debug/Trace.hs')
| -rw-r--r-- | libraries/base/Debug/Trace.hs | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/libraries/base/Debug/Trace.hs b/libraries/base/Debug/Trace.hs index 5a8b55126c..e85fb7590a 100644 --- a/libraries/base/Debug/Trace.hs +++ b/libraries/base/Debug/Trace.hs @@ -106,12 +106,13 @@ putTraceMsg = traceIO The 'trace' function outputs the trace message given as its first argument, before returning the second argument as its result. -For example, this returns the value of @f x@ but first outputs the message. +For example, this returns the value of @f x@ and outputs the message to stderr. +Depending on your terminal (settings), they may or may not be mixed. >>> let x = 123; f = show >>> trace ("calling f with x = " ++ show x) (f x) -"calling f with x = 123 -123" +calling f with x = 123 +"123" The 'trace' function should /only/ be used for debugging, or for monitoring execution. The function is not referentially transparent: its type indicates @@ -127,8 +128,8 @@ trace string expr = unsafePerformIO $ do Like 'trace' but returns the message instead of a third value. >>> traceId "hello" -"hello -hello" +hello +"hello" @since 4.7.0.0 -} |