So, using templates, we can write programs that do computation at compile time, such programs are called template metaprograms. Partial specialization used when arguments have a particular structure. Written by industry leaders, the book begins with the simplest of topics function templates and builds its way through the most daunting of topics to master partial specialization and metaprogramming. Since you dont have mutable variables available when youre programming with templates, its impossible to iterate over a sequence of values. Template metaprogramming is much more fun than mere generic classes. The reason is that tm can generate arbitrary code from the templates, but cannot modify the nontemplate code. Template metaprogramming 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. During this instantiation, factorial value will be instantiated. The basics template metaprogramming tmp arose by accident.
Metaprogramming allows programs to create methods on the fly instead of having to define them in the program itself. The call factorial value in line 1 causes the instantiation of the primary or general template in line 2. In many ways, that collection of templates was the precursor to the boost metaprogramming library mpl. Variablefunctions names i usually prefer to have only one of two possible public operations defined in a tmp class. Most people insist on trying to metaprogram from inside their favorite language.
In general, macros are frowned upon in this role and templates are preferred, although they are not as generic. Template metaprogramming often makes use of compiletime computations, whether via templates or constexpr functions. Metaprogramming or more specifically, template metaprogramming is the practice of using templates to create constants, functions, or data structures at compiletime. Download pdf c template metaprogramming book full free. Metafunction aka type traits is a template metaprogramming technique for type introspection, type manipulation and type computation. Weve had the idea of writing about template metaprogramming for. Need help mixing computed goto and loop unrolling via template metaprogramming. Literally, each of us may be our programs, nothing more, nothing less. The complete guide since it is also the definitive reference for templates in general. 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. This recursion will end if the fully specialised class template factorial kicks in in line 3. However, before you get visions in your mind of robots writing code to take over the world, understand that its actually much less intense.
None of us can escape our own nature as programmable entities. Technically metaprogramming is code that writes code. Programming and metaprogramming in the human biocomputer all human beings, all persons who reach adulthood in the world today are programmed biocomputers. Recently, however, ive faced a problem that could not be solved by the means outlined in the article. Lets cover variable templates first, because theyre a lot like class templates. Great introduction to c metaprogramming by simon tatham can be found here.
And inspiring introduction to template metaprogramming. Despite the extremely baroque nature of template metaprogramming, templates are used in fascinating ways that extend beyond the wildest dreams of the language designers 1. The chapter presents further examples for this usage as well. The rst article on template metaprogramming 7 was published in 1995.
Metaprogramming with templates yes, the code checks whether the number is a prime number template struct isprime2 static const int resisprime2 metaprogramming 7 was published in 1995. The two newer standards are not used in the code so that the examples can be rich, illustrate the. C template metaprogramming available for download and read online in other formats. This technique is called template metaprogramming tmp. Overloading function templates like ordinary functions, function templates can also be overloaded. Sep 09, 20 templates can be used to perform compiletime calculations on data that is known, of course, at compile time. It means that a program can be designed to read, generate, analyze or transform other programs, and even modify itself while running. Template metaprogramming is challenging enough without trying to generalize the class to support multiple operations.
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. Im going to start with an example from the ruby on rails framework. This section contains examples about template metafunctions. A complete mpl reference manual, in html and pdf form. That doesnt work if the language doesnt support metaprogramming well. In some cases, this can be used to optimize the eventual runtime of a program. An introduction to metaprogramming for scientific computing dr conrad sanderson senior research scientist version 1. Pdf c template metaprogramming download full pdf book.
Write high performance code by eliminating virtual member function calls. This allows computations to be performed once at compile time rather than at each run time. A way around this is to do metaprogramming from outside the language, using program transformation tools. Metaprogramming is a programming technique in which computer programs have the ability to treat other programs as their data. The if template was the rst control structure in a generic form 3 and the remaining control structures were published in 4. Not everyone needs to know or needs to use metaprogramming techniques to be a good programmer, and it might look like a. Originally, templates were designed to enable generic programming and provide type safety. Before going into the description of our obfuscator, it is necessary to give some basis of the mechanism involved. There have been some articles dealing with template metaprogramming before over here. This makes it possible to create a template which calculates a value at return time, a value which can then be used as a constant in the rest of the program. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext.
Template specialization a version of a template to use when a specific pattern of arguments are supplied. This post starts a series of articles following the contrived and tortuous path down insanity lane. Mos 4465a is an advanced financial ac modern advanced accounting in canada, 8th edition, mcgraw. Full specialization used when all arguments are specified. A metaprogram is a program that generates or manipulates program code.
The problems were solved by the traits template idiom see 3. The compiler must then decide which ones to use the rules of these decisions and how the compiler does this can get very complicated and lead to issues. Things like template, which look really weird but behave in an even more bizarre way. Metaprogramming in c is the art of creating new language constructs, typically using macros. The output of these templates include compiletime constants, data structures, and complete functions. For ease of use and to avoid this for simple templates we can use a header and an inline function. Perhaps surprisingly, in view of the fact that templates are functional programs, func. The use of templates can be thought of as compiletime execution. Concepts, tools, and techniques from boost and beyond pdf, epub, docx and torrent then this site is not for you.
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