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Questions tagged [macros]

***DO NOT USE for VBA / MS-Office languages. Use [vba] instead.*** A macro is a rule or pattern that specifies how a certain input sequence (often a sequence of characters) should be mapped to an output sequence (also often a sequence of characters) according to a defined procedure.

A macro is a rule or pattern that specifies how a certain input sequence (often a sequence of characters) should be mapped to an output sequence (also often a sequence of characters) according to a defined procedure. The mapping process that instantiates (transforms) a macro into a specific output sequence is known as macro expansion.

Wikipedia Article for Macro

'Macros' created in VBA/MS-Office applications, while sharing the same name, are not the same concept as defined here. Questions relating to VBA should be tagged and the respective Office-Product, e.g. , . Please see the tag wiki entry page for more information regarding proper usage.

Similarly, questions relating to other macro programming languages should not use this tag.

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When should I quote CMake variable references?

I am writing CMake macros for the first time, and I have a hard time understanding how variables work. Most specifically, ${a} seems to have a different meaning than "${a}". For example here: Passing a list to a CMake macro When am I supposed to add…
Vince
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Collection of Great Applications and Programs using Macros

I am very very interested in Macros and just beginning to understand its true power. Please help me collect some great usage of macro systems. So far I have these constructs: Pattern Matching: Andrew Wright and Bruce Duba. Pattern matching for…
unj2
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How do I check for C++20 support? What is the value of __cplusplus for C++20?

Related to questions How do I check for C++11 support? and What is the value of __cplusplus for C++17? How can I inquire whether the compiler can handle / is set up to use C++20? I know that it is, in principle, possible to inquire the C++ version…
user2296653
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Which Cross Platform Preprocessor Defines? (__WIN32__ or __WIN32 or WIN32 )?

I often see __WIN32, WIN32 or __WIN32__. I assume that this depends on the used preprocessor (either one from visual studio, or gcc etc). Do I now have to check first for os and then for the used compiler? We are using here G++ 4.4.x, Visual Studio…
math
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Which macro to wrap Mac OS X specific code in C/C++

While reading various C and C++ sources, I have encountered two macros __APPLE__ and __OSX__. I found plenty of use of __OSX__ in various codes, especially those originating from *BSD systems. However, sometimes I find that testing __OSX__ only is…
mloskot
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Retrieving a c++ class name programmatically

I was wondering if it is possible in C++ to retrieve the name of a class in string form without having to hardcode it into a variable or a getter. I'm aware that none of that information is actually used at runtime, therefor it is unavailable, but…
Morgan
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What does #x inside a C macro mean?

For example I have a macro: #define PRINT(int) printf(#int "%d\n",int) I kinda know what is the result. But how come #int repersent the whole thing? I kinda forget this detail. Can anybody kindely give me a hint? Thanks!
Anders Lind
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What is double evaluation and why should it be avoided?

I was reading that in C++ using macros like #define max(a,b) (a > b ? a : b) can result in a 'double evaluation'. Can someone give me an example of when a double evaluation occurs and why it's bad? P.S.: Surprisingly I couldn't find any detailed…
AnkithD
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What is the value of __cplusplus for C++17?

We are trying to test some code under C++17 and its change to std::uncaught_exception. I can't seem to get GCC to provide the value of __cplusplus: $ /opt/local/bin/g++ -std=c++17 -dM -E -
jww
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Can I have macros in Java source files

In my program I'm reading integers form console many times. Every time, I need to type this line. new Scanner(System.in).nextInt(); I'm used to C/C++ and I'm wondering if I can define something like #define READINT Scanner(System.in).nextInt();…
Muthu Ganapathy Nathan
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How to use __DATE__ and __TIME__ predefined macros in as two integers, then stringify?

Want to use __ DATE __ and __ TIME __ as integer for giving automated version to my code in compile time. #define STRINGIZER(arg) #arg #define STR_VALUE(arg) STRINGIZER(arg) #define DATE_as_int_str useD(__DATE__) // What can be done…
Rick2047
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error: pasting "." and "red" does not give a valid preprocessing token

I'm implementing The X macro, but I have a problem with a simple macro expansion. This macro (see below) is used into several macros usage examples, by including in this article. The compiler gives an error message, but I can see valid C code by…
Jack
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Why use Macros in C?

Possible Duplicate: What are C macros useful for? Every few months I get an itch to go learn some bit of C that my crap college programming education never covered. Today it's macros. My basic understanding of macros is they're a simple search…
Alana Storm
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Can I convert a string to enum without macros in Rust?

For example, if I have code like: enum Foo { Bar, Baz, Bat, Quux } impl Foo { from(input: &str) -> Foo { Foo::input } } This will obviously fail because input is not a method of Foo. I can manually type: from(input:…
bright-star
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Why aren't there macros in C#?

When learning C# for the first time, I was astonished that they had no support for macros in the same capacity that exists in C/C++. I realize that the #define keyword exists in C#, but it is greatly lacking compared to what I grew to love in C/C++.…
Andrew Garrison
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