Also, for some history, this was discussed a while back: http://www.mail-archive.com/haskell@haskell.org/msg03721.html Thanks for pointing me to earlier discussions on this subject - they are enlightening :) One particular argument "against" seems to be very convincing to me:
"From a language design point of view, it should be noted that turning non-left linear patterns into ones with == guards elevates the class Eq to built-in status - but the compiler has no semantic control over it." I see there are many things I didn't consider (and many more that I don't even understand). So is there some recommended reading on the subject of linear patterns? Most of all I'm wondering why they are called "linear"? Regarding the possibility of making accidental mistakes during refactoring etc. This could be implemented as a language extension, requiring explicit LANGUAGE pragma. So people using it would know they have semantics slightly changed and need to be aware that there is a possibility of making these kind of mistakes. Janek