[boost] [Review:Algorithms] Order of args to clamp

Subject: [boost] [Review:Algorithms] Order of args to clamp
From: Phil Endecott (spam_from_boost_dev_at_[hidden])
Date: 2011-09-23 12:21:23

Dear All,

Some quick comments about the proposed clamp() function:

   template<typename V>
   V clamp ( V val, V lo, V hi );

I have a clamp function that orders the args low - middle - high, which 
seems like a more natural ordering to me.  Is there some rationale or 
precedent for this middle - low - high ordering?  I think the confusion 
matters in this case because type checking won't help to detect 
mistakes, and in the most obvious applications (e.g. sanitising input) 
it might be hard to spot an error.  (In contrast, 
max(low,min(mid,high)) is unambiguous and not much more typing...)

I note that this function takes its args by value, while std::min & max 
take const references.  What is the rationale for this?

Like min & max, clamp has a single type template parameter; what are 
the implications of this?  For example, if I pass a mixture of 
std::string and const char* arguments, what will happen? Ideally, (a) 
all combinations would compile, and (b) conversions from const char* to 
std::string will only happen when necessary, not unconditionally for 
all of the arguments.  (Maybe that is asking too much, though.)

Regards,  Phil.