The MPL documentation is better than before and the reference is excellent. However I do not believe the tutorial is adequate for bringing new programmers interested in understanding metaprogramming using MPL into a general understanding of how MPL works and how to use it. This is because the tutorial does not start at the beginning of defining MPL concepts but jumps into high order metafunctions without explaining the basis of metafunctions or metaprogramming classes to begin with. I understand the problem, that metaprogramming is a large concept and that understanding the basics would entail starting at a point where explaining anything further takes up much more space than a mere tutorial would normally encompass. The answer no doubt is to buy Mr. Abrahams and Mr. Gurtovoy's book. However despite the good intent of the tutorial, I think that it only performs the function of bringing further knowledge of the MPL library to those who already understand how the basics of the library already work. For those C++ programmers who want to learn to understand how to use the MPL library from scratch, I do not think the tutorial is adequate. Perhaps MPL was never meant to appeal to those without a knowledge of its precepts to begin with, but by assuming that I think that the tutorial will either leave C++ programmers who would like to learn to use MPL feeling pretty cold about it, or force them to buy the book in order to understand how it works.
"Edward Diener" <eddielee@tropicsoft.com> writes:
That's because it's not a tutorial. It's really just a chapter from the book that's been lifted. Aleksey and I had some disagreement about calling it a "tutorial."
I think it's a reasonable answer. An online reference manual for an STL implementation shouldn't be expected to explain generic programming, and an online reference for an OO GUI framework shouldn't be expected to explain OO.
Oh come now. Someone who know C++ well but doesn't already understand the basics of library won't be helped *at all* by this document? That's really hard to believe. It provides significant explanation, example, and walkthrough material.
Perhaps so.
It's not intended to force anything. I hope it isn't viewed as a cynical attempt to generate book sales, because including it and labelling it a tutorial was really a last-minute choice designed to (partially) fill an obvious gap. -- Dave Abrahams Boost Consulting http://www.boost-consulting.com
David Abrahams wrote:
I vote for whoever feels it should not be called a tutorial, which I guess is you rather than Aleksey. But in keeping with the efforts of Boost library implementors to provide either a generalized tutorial, or an overview of functionality, I think either should be offered rather than a chapter from your book.
An online reference for a GUI framework should be expected to explain the basic structure of the GUI framework, and how to use it, before it denotes the class structure of that framework. Perhaps this explanation of the basics should be called an overview.
It is clearly now what I said that "Someone who know C++ well but doesn't already understand the basics of library won't be helped *at all* by this document". The tutorial provides significant information and is very well written. But it starts somewhere beyond the beginning of the subject matter. To you and Aleksey, and probably to those who have already been using the MPL library such as many current developers, the beginning understanding is already known. To those first starting with the MPL, even those with template programming experience, I do not believe that is the case. While I think that I may be able to understand enough from your tutorial to fill out the missing pieces of what is probably chapters 1 and 2 of your book, try considering whether this is the case for everyone else. Furthermore do you want it to be the case ? Wouldn't it be better to provide a real overview, or tutorial if you like, that would explain the general concepts of MPL from the beginning and then rely on the programmer to figure out the rest through their use of it and the documentation in the reference section ?
I certainly do not view it is an attempt, cynical or otherwise, to generate sales. In fact by offering an entire, and evidently key, chapter from your book, you will probably hurt your sales <g>. By "force them to buy the book" I merely meant that the information from then first few chapters probably provides the necessary conceptual groundwork for understanding the library which a C++ programmer may need. We can argue all day whether the tutorial provides a good enough explanation for your fairly intelligent C++ programmer who understands the basics of programming template functions and classes, as opposed to just using them, to understand how to use the MPL to do template metaprogramming, but I think if you honestly ask yourself whether a better overview, or tutorial if you like, is needed which makes it easier for the novice template metaprogrammer to use the MPL, your answer will be yes. As far as the writing, and explanation in the tutorial you provide, it is quite good and I am not questioning that. Perhaps the idea is to summarize the beginning information in chapters 1 and 2 in your book briefly and then present chapter 3 as you have done.
"Edward Diener" <eddielee@tropicsoft.com> writes:
Fortunately neither of us is running for office (as far as I know) ;-).
I agree. There wasn't time for this release... and after writing the book I'm not sure if either one of us is motivated enough to do it soon.
Yeah, and I think that omitting some mention of the relationship to the STL on the front page of the docs was a mistake.
and how to use it,
I do think the Metafunctions chapter does that.
before it denotes the class structure of that framework. Perhaps this explanation of the basics should be called an overview.
Sounds good to me.
No, to quote: ...I think it only performs the function of bringing further knowledge of the MPL library to those who already understand how the basics of the library already work. which means that you think that chapter will bring no further knowledge of MPL to anyone who hasn't seen the MPL before. I just think that's a gross exaggeration, if not an outright falsehood.
The tutorial provides significant information and is very well written.
Thank you.
But it starts somewhere beyond the beginning of the subject matter.
Yes. It's chapter 3 in the book.
Correct. But the "what is metaprogramming?" and "why metaprogramming?" questions really should be left to the book. And the 2nd chapter in the book describes traits and type manipulation, and shows how simple generic programming problems can be solved using the Boost Type Traits library. I can't imagine what to do on the Boost website other than say, "if you have no idea what this is, you probably should get familiar with Boost.Type Traits and think about how type information can be useful in your programs..." but at that point, well, the next step ought to be the book. So if you have specific ideas about what should be covered in such an overview, in such a way that it doesn't become our book all over again, I'm all ears.
I'm sure it isn't the case for everyone else.
Not sure what "from the beginning" means. That chapter does explain the general concepts of MPL, except for one crucial concept that really needs to be filled in before you can understand it. It's really a glaring omission that the "tutorial" doesn't describe what a _Metafunction_ is.
That's not the case.
I don't think it does (and never claimed it did). Probably if you fill in the missing definition of _Metafunction_ it would serve pretty well, though.
You are correct. That was part of my objection to calling that chapter a tutorial.
Here is the detailed TOC for the first 2 chapters. Most of what's covered in chapter 1 should be clear from what's shown below. The discussion of alternatives (5.1/5.2) examines strategies other than metaprogramming and analyzes their advantages and disadvantages. Most of chapter 2 is built around a look at how type information can be used to implement std::iter_swap effectively. But, crucially, it also introduces metafunctions. I honestly don't see how to summarize these things. We made a huge effort in the book to be concise. For someone who doesn't know what's going on already, there isn't much that can be pruned. o Introduction 1 Getting Started 2 So What's a Metaprogram? 3 Metaprogramming in the Host Language 4 Metaprogramming in C++ 4.1 Numeric Computations 4.2 Type Computations 5 Why Metaprogramming? 5.1 Alternative 1: Runtime Computation 5.2 Alternative 2: User Analysis 5.3 Why C++ Metaprogramming? 6 When Metaprogramming? 7 Why a Metaprogramming Library? o Traits And Type Manipulation 1 Type Associations 1.1 Using a Direct Approach 1.2 Taking the Long Way Around 1.3 Finding a Shortcut 2 Metafunctions 3 Numerical Metafunctions 4 Making Choices at Compile Time 4.1 More iter_swap 4.2 A Fly in the Ointment 4.3 Another Fly! 4.4 The Flyswapper 5 A Brief Tour of the Boost Type Traits Library 5.1 General 5.2 Primary Type Categorization 5.3 Secondary Type Categorization 5.4 Type Properties 5.5 Relationships Between Types 5.6 Type Transformations 6 Nullary Metafunctions 7 Metafunction Defintion 8 History 9 Details 10 Exercises -- Dave Abrahams Boost Consulting http://www.boost-consulting.com
David Abrahams wrote:
From these topics I would guess that a good overview before your chapter 3 would entail a basic explanation of:
1.4.1 1.4.2 2.2 2.3 2.6 2.7 and anything related to them regarding values and types you want to say. I would leave out all but the simplest examples showing exactly what you mean and just explain the ideas. What I am simple saying is that if you want to make it fairly easy for the non-experienced MPL programmer to pick up the MPL library you will include some material about the information above. I could even say to you, although it is purely your and Mr. Gurtovoy's choice, that you might think of making chapters 1 and 2 available online as you have chapter 3. Of course you may well feel that by doing this you are giving away what you feel you should earn via book sales, as well it may be that your book contract does not allow this anyway. I do think that it is possible to understand your MPL library without the information in chapters 1 and 2, but that it becomes more difficult, and more work, for the beginning MPL programmer to do so. Personally I get discouraged when documentation does not give me a good overview of concepts, not because I think that I can not pick up the information if I were willing to investigate and work at it but because I get annoyed that those who are doing good work are not providing me with the information I need to make learning easier. Perhaps I am not in the majority, but my view of the importance of good documentation is not that of the majority either. I realize that both you and Mr. Gurtovy may be tired of explaining MPL now that you have written a book about it, and documented it in the Boost MPL reference, to write anything more. I can only say to you that you put yourself in the place of programmers who may be interested in your ideas, who are intelligent, who follow the Boost libraries, but do not know what you do about metaprogramming and how you designed the library to make it easier for people to metaprogramming in C++. If you think you have given enough, fine. If not, consider one more effort at a basic number of pages of introduction, perhaps very few in number and very basic, which leads programmers to be interested in your ideas. Thanks for listening !
"Edward Diener" <eddielee@tropicsoft.com> writes:
That looks good.
That's what we thought we were doing in the book! ;-) Concision is hard.
It's not up to us; Addison-Wesley owns the material and I doubt they'd be willing to let us do that.
Bingo.
I agree.
It is reasonable to expect the basic concepts to be defined.
I little.
If you include the book, I think we have. But I do think the website needs to cover a few of the basic concepts we've left out. I even think it would help book sales to include more information.
Whew. I wonder when there will be time? -- Dave Abrahams Boost Consulting http://www.boost-consulting.com
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