On Wed, 29 Feb 2012 18:13:30 -0600, Richard van Scheijen <dl...@mesadu.net> 
wrote:

When logging the severity level should convey a certain insight
that the developer has about the code. This can be done with a 3
bit field. These are: known-cause, known-effect and breaks-flow.

This creates the following matrix:

KC KE BF Severity
=================
1  1  0  Trace
0  1  0  Info
1  0  0  Notice
0  0  0  Warning
1  1  1  Error
0  1  1  Critical
1  0  1  Severe
0  0  1  Fatal

A known cause is when the developer knows why a log event is
made. e.g.: if you cannot open a file, you do not know why.
A known effect is when he/she knows what happens after.
Basically, you can tell if it is a catch-all by this flag.

When a severity should only be handled by a debugger, the normal
debug statement should be used. This is in essence a 4th bit.

I hope this helpful in the search for a good level system.


vote++

I think establishing a good guideline as to log usage should be part of 
std.log's documentation. Making the bitflags a part of Severity might help 
cement this concept. It would also allow self documenting code, like:

log!(knownCause|unknownEffect|breaksFlow)("This is a severe message.");

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