Henning Thielemann writes:
One advantage is that you need to type fewer characters.
I know memory is expensive, that's why only the last two digits of year numbers are stored. :-]
I understand what you're getting at -- and I find it annoying, too, when people sacrifice robustness for comfort. I'm not sure, though, whether this is the case here, because vsnprintf in Haskell still is type-safe. You'll get more complicated error messages, the memory footprint might be worse, but it still _is_ robust code. Perhaps it really is a matter of personal taste. Just for the sake of seeing the point from all possible perspectives, I could think of another reason why you might need a function like that: If you want to provide printf-style variable substitutions to the user, say in a config file. People are _used_ to this mechanism, and many programs I know offer this feature to customize text templates, etc. It can't hurt to have a function that does the parse job and returns the result for you. Although, if you think this through, you'll soon arrive at the conclusion that for this particular use-case hard-coded place-holders (like %s, %d, etc.) are not that useful. You'd like to be able to (easily!) extend the function, to offer a more general variable substitution, like sh(1) does. So that you could write Dear ${customer}, are you interested in making ${phantasy-number} fast? and pass a function (String -> a) to vsnprintf which does the lookup. I'm not sure how having different types of values in the dictionary plays into this, though.
You can save even more characters:
msg = verb "i = " . shows 12 . verb "\tj = " $ "test"
Right! One more reason to use ShowS-style. :-) Peter