Re: Understanding MPL

From: Edward Diener (eddielee_at_[hidden])
Date: 2003-04-04 17:40:57

Paul Mensonides wrote:
> Edward Diener wrote:
>
>> The doc needs to be rewritten and presented in a logical manner to
>> those who are coming to the pp-lib for the first time and are trying
>> to understand its purpose and what problems it hopes to solve or what
>> programming tasks it hopes to make easier.
>
> These are all completely open-ended and naive questions.  There
> already are examples of problems that have been solved with the
> pp-lib, yet you say you don't like learning from examples.  However,
> these are just a few possibilities. One of the primary uses of the
> pp-lib today is repetition of various kinds (the primary use by the
> Python library and the MPL is in this area), but that is only a small
> portion of the library.  The question of applicability is incredibly
> context sensitive.  I guess my advice in this regard is simple, if it
> cannot be done reasonably with template metaprogramming, examine
> whether it is possible to do it with preprocessor
> metaprogramming--where "it" is a placeholder for whatever you might
> want to do at compile-time.  There are, of course, limitations to
> both template metaprogramming and preprocessor metaprogramming, but
> only experience with both can tell you whether something is doable or
> not or how it might be done.
>
>> The various macros need to
>> be grouped in categories which make it easier to understand what
>> functionality exists and why.
>
> These are the categories that actually exist:
>
> - Unsigned saturation arithmetic in the range of 0 to 256.
> - Manipulation of the "array" data type.
> - Unsigned numeric comparisons in the range of 0 to 256.
> - Control flow constructs (such as 'if', 'while', etc.)
> - Vertical repetition (a.k.a. iteration)
> - Manipulation of the "list" data type.
> - Logical operations such as 'and' and 'or'.
> - Punctuation operators for problem characters like commas and
> parentheses.
> - Horizontal repetition constructs
> - Manipulation of the "sequence" data type.
> - Evaluated slots.
> - Manipulation of the "tuple" data type.
>
> ...and a host of other non-groupable macros.

It would be a good start to discuss the various categories as subjects of
documentation, and illustrate that subject by specifying the various macros
which belonged to each category. That way an end-user could gain some idea
of the functionality in the pp-lib by a breakdown into manageable ideas and
uses. I realize that categories might overlap each other and some categories
might need extended discussion while others would need a very short
explanation. But breaking down the pp-lib into understandable topics of
functionality would make it understandable to the end-user to a much greater
degree than just a long alphabetical list of macros which the present
documentation presents.

I am not trying to cause unnecessary documentation work for you or anybody
else in rewards to the pp-lib. If I am the only one having a really hard
time attempting to grasp what is there I would say to not do anything
further with the current doc. But I have a feeling that their are other
programmers who would greatly benefit from a more understandable
presentation of the Boost pp-lib functionality. I am willing to tackle the
complications of macro expansion and the issues which cause the library to
be created the way that it does, if I can feel that the functionality behind
it is understandable and useful to me as a programmer.