The ability to generate code at compile time allows the programmer to implement such features as polytypic programs, macrolike. So far weve learned the basic constructs of template metaprogramming loops, branching, return values and some basic list operations getting the length of a list, appending and prepending elements, checking if an element is included in a list. Template metaprograms can generate useful code when interpreted by the compiler, such as a massively inlined algorithm that is, an implementation of an algorithm which works for a specific input size, and has its loops unrolled. The addition of staticif would make it much cleaner. Unrolling and simplifying expressions with template haskell, by. Both expressions have the same meaning and behave in exactly the same way. Weve had the idea of writing about template metaprogramming for.
Template metaprogramming is turingcomplete, meaning that any computation expressible by a computer program can be computed, in some form, by a template metaprogram. Metaprogramming with templates yes, the code checks whether the number is a prime number template jun 11, 2015 for the love of physics walter lewin may 16, 2011 duration. Therefore, i call this projecttechnique template metaprogramming programming. Function templates are special functions that can operate with generic types. The output of these templates include compiletime constants, data structures, and complete functions. May 26, 2016 its no more difficult conceptually than haskell or some other first order language.
These pioneers greatly influenced the field, and basically what should be written is now written. The complete guide by david vandevoorder and nicolai m. Lets explore template metaprogrammingwith a couple of code. It was not designed to be a first order language, so the syntax is very cumbersome 2. Template metaprogramming is in fact turingcomplete, meaning that any computation expressible by a computer program can be computed, in some form, by a template metaprogram.
With variadic templates, parameter packs and template aliases. It seems really cool, make the compiler do most of the work. The latter form was introduced to avoid confusion, since a type parameter need not be a class. Mos 4465a is an advanced financial ac gold advanced maximiser with key. While i consider myself falling rather in the camp of the aficionados, ive met a lot more people that dont have a strong interest for it, or that even find it downright disgusting, than tmp enthusiasts. An introduction to metaprogramming for scientific computing dr conrad sanderson senior research scientist version 1. A template parameter is a special kind of parameter.
Template metaprogramming is generally not used in practical programs, it is an interesting conecpt though. That doesnt work if the language doesnt support metaprogramming well. When c was developed, maths libraries implemented functions. Parsing, compiling, and static metaprogramming jsconf eu 20 duration.
For the love of physics walter lewin may 16, 2011 duration. There have been some articles dealing with template metaprogramming before over here. Template metaprogramming for haskell, by tim sheard and simon peyton jones, oct 2002. We can all learn enough to use it in our daytoday coding. Most ebooks are available as drmfree epub, mobi, and pdfall together for one price so you can learn on your desktop or preferred device.
For example, a software company may need sort for different data types. Its no more difficult conceptually than haskell or some other first order language. I was motivated to write this after i read eric nieblers thoughtprovoking tiny metaprogramming library article. This allows us to create a function template whose functionality can be adapted to more than one type or class without repeating the entire code for each type. The first metaprogram history is just on damn thing after another nicolas cage inspiring.
It allows even inexperienced programmers to perform compiletime computations without doing any tmp on the surface. Template metaprogramming for haskell microsoft research. A macro is a piece of code that executes at compile time and either performs textual manipulation of code tobe compiled e. Template metaprogramming scuola superiore santanna. However, before you get visions in your mind of robots writing code to take over the world, understand that its actually much less intense. An introduction to template metaprogramming barney dellar software team lead toshiba medical visualisation systems. The ability to generate code at compile time allows the programmer to implement such features as polytypic programs, macrolike expansion, user directed optimization such. The basics template metaprogramming tmp arose by accident. Template metaprogramming is a generic programming technique that uses extremely early binding. C is ideally suited to modern computers and modern programming. Template metaprogramming tmp is a metaprogramming technique in which templates are used by a compiler to generate temporary source code, which is merged by the compiler with the rest of the source code and then compiled. Its aim is to teach c to a beginner, but with enough of the details so as not be outgrown as the years go by. Metaprogramming or more specifically, template metaprogramming is the practice of using templates to create constants, functions, or data structures at compiletime.
The if template was the rst control structure in a generic form 3 and the remaining control structures were published in 4. The purpose of the system is to support the algorithmic construction of programs at compiletime. Things like template, which look really weird but behave in an even more bizarre way. Sep 09, 20 in some cases, this can be used to optimize the eventual runtime of a program. Concepts, tools, and techniques from boost and beyond pdf, epub, docx and torrent then this site is not for you.
Template metaprograms are often hard to comprehend, and i must warn you that this may well apply to many of the codeblocks in this article. Hana libraries, and functional reactive programming with the rxcpp. Tmp doesnt have branching, so we use specialization. Textual macros are macros that directly affect the text of the programming language without knowing about or dealing with the meaning of the language. This technique is called template metaprogramming tmp. This post starts a series of articles following the contrived and tortuous path down insanity lane. I have very simple program that uses tmp,it calculates the square of a number, but it doesnt seem to. Concepts, tools, and techniques from boost and beyond pdf,, download ebookee alternative practical tips for a improve ebook reading. Grab it directly from the iterator c deref, parent, visitcount grab the first value from the subtree contained in the iterator c deref. Metaprogramming with templates yes, the code checks whether the number is a prime number template struct isprime2.
Jun 21, 2015 template metaprogramming tmp is a metaprogramming technique in which templates are used by a compiler to generate temporary source code, which is merged by the compiler with the rest of the source code and then compiled. Lets explore template metaprogrammingwith a couple of code examples. A class template is instantiated by passing a given set of types to it as template arguments. Advanced by edwards, lynda cambridge english advanced certificate in. Technically metaprogramming is code that writes code. This allows computations to be performed once at compile time rather than at each run time.
The rst article on template metaprogramming 7 was published in 1995. Techniques for making the mpl work on vc6vc7borlandgcc2. A way around this is to do metaprogramming from outside the language, using program transformation tools. Your contribution will go a long way in helping us serve. We propose a new extension to the purely functional programming language haskell that supports compiletime metaprogramming. So, in metaprogramming, we create code that will run when the code is compiled. And inspiring introduction to template metaprogramming. Caveat i decided to do this talk after getting thoroughly lost on the recent talk on sfinae. I have a lot of convoluted template code with sfinae and specialization that is awful to read and write. Oct 20, 2005 the c preprocessor cpp first lets look at metaprogramming that involves textual macro languages. Plus there are some things that could be done with staticif that cannot be done currently with templates due to the intricacies of how it works or they could just relax some of the. The simple idea is to pass data type as a parameter so that we dont need to write the same code for different data types.
Rather than writing and maintaining the multiple codes, we can write one sort and. Concepts, tools, and techniques from boost and beyond book. Your price below reflects our everyday 20% off savings. Most people insist on trying to metaprogram from inside their favorite language. Template metaprogramming is the practice of using templates to generate types and functions to perform computations at compiletime and generate programs. What weve done now is program a little function or subroutine that is evaluated compiletime, using tmp. The two most widely used textual macro systems are the c preprocessor and the m4 macro processor. The compiler acts as an interpreter or a virtual computer that emits the instructions that make up the final program. C deref this specialization is only for leaf nodes.