Re: [Boost-users] [heap] Mix use of size_t and size_type

Subject: Re: [Boost-users] [heap] Mix use of size_t and size_type
From: Gavin Lambert (gavinl_at_[hidden])
Date: 2015-03-11 19:06:46

On 12/03/2015 01:02, Ben Pope wrote:
> On Wednesday, March 11, 2015 12:09 PM, Cheng Mo wrote:
>>  >Hi,
>>  >While reading d_ary_heap.hpp from the heap library I was surprised to
>>  >see a mix of size_t and size_type variables in an index computation
>>  >(https://github.com/boostorg/heap/blob/master/include/boost/heap/d_ary_heap.hpp#L356):
>>
>>  >    size_type last_child_index(size_type index) const
>>  >    {
>>  >        const size_t first_index = first_child_index(index);
>>  >        const size_type last_index = (std::min)(first_index + D - 1,
>>  >size() - 1);
>>  >        return last_index;
>>  >    }
>>  >Isn't this a typo?
>
> Looks wrong to me, arithmetic should probably use the same types.

Agreed.

> And what's going on with std::min?

I'm not sure what D is, but that's a fairly basic "constrain to no later 
than the end of the array" construct.

If you're referring to the parentheses around std::min itself, that's a 
standard defense against #define min().

You might also see this in some code as "std::min 
BOOST_PREVENT_MACRO_SUBSTITUTION (...)", which is more obvious but also 
much uglier.