Re: [boost] Review Request: Creasing (Sequence Properties)

Subject: Re: [boost] Review Request: Creasing (Sequence Properties)
From: Joachim Faulhaber (afojgo_at_[hidden])
Date: 2010-01-27 17:25:20

2010/1/27 Stewart, Robert <Robert.Stewart_at_[hidden]>:
> Joachim Faulhaber wrote:
>>
>> 'is_sorted' is an important predicate. But it lives as an invariant
>> to be maintained rather than a function to computed. So we have
>> happily coded all kinds of sorted things without explicitly using
>> and not necessarily needing it.
>>
>> My question: Other than inside BOOST_ASSERTS, where do we really
>> need is_sorted in production code. Are there convincing use cases?
>
> That's an excellent question.  I, too, foresaw its usefulness in assertions.
> I can imagine those doing DBC would like it, too.  However, I can imagine
> examining file, network, or user input to ensure the data fits some ordering
> criteria, too.

. . . more of the (initially) asserting-the-invariant type of use.

Yet, the question no longer is: Is "is_sorted" (aka is_ordered, is_creasing)
an important predicate, that needs to be included into boost algorithms,
because *it already is*. As Grant hinted there is boost::is_sorted in
boost/detail/algorithm.hpp. Moreover std::is_sorted is in the sgi-stl
and std::is_sorted will probably be in the new standard (see N3000):
So is_creasing is ceasing I dare say.

Remains the question, if the variants of is_[strictly_]{in_,de_}creasing
are to be added as algorithms, which conjures up another intersting
question:

Are there criteria to be fulfilled to maintain the minimality of a set of
free algorithms?

Regards,
Joachim