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.
macros
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questions
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Add preprocessor macro to a target in xcode 6
Probably this is pretty simple, but I can't find a way to define a preprocessor macro for a target in Xcode 6.
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43
votes
1
answer
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What does the tt metavariable type mean in Rust macros?
I'm reading a book about Rust, and start playing with Rust macros. All metavariable types are explained there and have examples, except the last one – tt. According to the book, it is a “a single ...
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votes
2
answers
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Expand macros inside quoted string [duplicate]
Possible Duplicate:
C Macros to create strings
I have a function which accepts one argument of type char*, like f("string");
If the string argument is defined by-the-fly in the function call, ...
- 2,142
43
votes
9
answers
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macro definition containing #include directive
Is there a way to define a macro that contains a #include
directive in its body?
If I just put
the "#include", it gives the error
C2162: "expected macro formal parameter"
since here I am not using #...
- 1,024
43
votes
7
answers
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views
When was the NULL macro not 0?
I vaguely remember reading about this a couple of years ago, but I can't find any reference on the net.
Can you give me an example where the NULL macro didn't expand to 0?
Edit for clarity: Today it ...
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43
votes
6
answers
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Python-like C++ decorators
Are there ways to decorate functions or methods in C++ like in python style?
@decorator
def decorated(self, *args, **kwargs):
pass
Using macros for example:
DECORATE(decorator_method)
int ...
- 1,927
43
votes
3
answers
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Can you capitalize a pasted token in a macro?
In a C macro, is it possible to capitalize a pasted-in token? For example, I currently have the following macro:
#define TEST(name, keyword) \
test_##name:
TEST_##keyword##_KEYWORD
I ...
- 1,563
42
votes
4
answers
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Macros for GCC/G++ to differentiate Linux and Mac OSX?
Macros for GCC/G++ to differentiate Linux and Mac OSX?
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42
votes
5
answers
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Is it possible to place a macro in a namespace in c++?
My application uses another output than the standard output for logging information, which is why I wrote my own Log(), Error(), Panic() and Assert() functions. To organize things nicely, I enclose ...
- 3,835
42
votes
1
answer
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Static return type of Scala macros
So I've got this macro:
import language.experimental.macros
import scala.reflect.macros.Context
class Foo
class Bar extends Foo { def launchMissiles = "launching" }
object FooExample {
def foo: ...
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41
votes
8
answers
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The need for parentheses in macros in C [duplicate]
I tried to play with the definition of the macro SQR in the following code:
#define SQR(x) (x*x)
int main()
{
int a, b=3;
a = SQR(b+5); // Ideally should be replaced with (3+5*5+3), ...
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41
votes
1
answer
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What is "with-eval-after-load" in Emacs Lisp
I came across the macro with-eval-after-load when trying to install persp-mode from here. But I am unable to find the macro inside Emacs and/or on Google. Where is it defined? Is it part of standard ...
- 21.3k
41
votes
2
answers
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Where can I learn about constructing AST's for Scala macros?
Where I can learn how to construct the AST's that Scala's macros generate?
The Scaladoc isn't as helpful as I'd like. For example:
abstract def Apply(sym: Universe.Symbol, args: Universe.Tree*): ...
- 45.4k
41
votes
3
answers
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How to prefix/suffix identifiers within a macro? [duplicate]
When using a macro that defines a function, is it possible to add a prefix to the function?
macro_rules! my_test {
($id:ident, $arg:expr) => {
#[test]
fn $id() {
...
- 45k
40
votes
3
answers
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C macro: #if check for equality
Is there a way to do check for numerical equality in macros?
I want to do something like
#define choice 3
#if choice == 3
....
#endif
#if choice == 4
...
#endif
Does C macros have support for ...
- 41.8k
40
votes
9
answers
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Inline function v. Macro in C -- What's the Overhead (Memory/Speed)?
I searched Stack Overflow for the pros/cons of function-like macros v. inline functions.
I found the following discussion:
Pros and Cons of Different macro function / inline methods in C
...but it ...
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votes
5
answers
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How do you implement header guards, and what can you put between them?
At LearnCpp.com | 1.10 — A first look at the preprocessor. Under Header guards, there are those code snippets:
add.h:
#include "mymath.h"
int add(int x, int y);
subtract.h:
#include "...
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39
votes
9
answers
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views
How to write macro for Notepad++?
I would like to write a macro for Notepad++ which should replace char1, char2, char3 with char4, char5, char6, respectively.
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1
answer
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How does Q_FOREACH (= foreach) macro work and why is it that complex?
In Qt, there is a foreach loop which is implemented using macros (Q_FOREACH). There are different implementations, depending on the compiler.
The definition for GCC is as follows:
#define Q_FOREACH(...
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votes
3
answers
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Is there a macro definition to check the Linux kernel version?
I'm wondering if there is a gcc macro that will tell me the Linux kernel version so I can set variable types appropriately. If not, how would I go about defining my own macro that does this?
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6
answers
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Is there a way to both check a macro is defined and it equals a certain value at the same time
I regularly use object-like preprocessor macros as boolean flags in C code to turn on and off sections of code.
For example
#define DEBUG_PRINT 1
And then use it like
#if(DEBUG_PRINT == 1)
...
- 1,801
39
votes
4
answers
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Equivalents to MSVC's _countof in other compilers?
Are there any builtin equivalents to _countof provided by other compilers, in particular GCC and Clang? Are there any non-macro forms?
- 115k
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votes
3
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When do we need #ifdef before #undef?
In many of the C and C++ files I have seen macros like this:
#ifdef X
#undef X // no statements in between
#endif
I feel that, it's adequate to simply write:
#undef X
If the macro X wasn't ...
- 69k
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votes
8
answers
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Debug Print Macro in C?
in C, what is the proper way to define a printf like macro that will print only when DEBUG symbol is defined?
#ifdef DEBUG
#define DEBUG_PRINT(???) ???
#else
#define DEBUG_PRINT(???) ???
#endif
...
- 381
38
votes
6
answers
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views
Visual Studio macro to find a string and delete matching lines
In my Visual Studio (2010 C#) solution, I need to delete all lines of code that contain a matching string pattern.
For example, I want to delete all lines that contain ".BackColor = System.Drawing....
- 465
38
votes
2
answers
10k
views
What's the easiest way to use reify (get an AST of) an expression in Scala?
I'm looking at alternatives to -print or javap as a way of figuring out what the compiler is doing in Scala. With the new reflection/macros library, reify seems a good candidate for that, as shown in ...
- 296k
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votes
5
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Can I comment multi-line macros?
I'm writing a few large macros and thought it'd be nice if I could add comments to them, like this:
#define SOME_BIG_MACRO(input)\
SOME_FUNCTION_CALL() \ // this does...
SOME_OTHER_FUNCTION_CALL()...
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2
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Detecting Integer Constant Expressions in Macros
There was a discussion in the Linux kernel mailing list regarding a macro that tests whether its argument is an integer constant expression and is an integer constant expression itself.
One ...
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votes
3
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What is the difference between a preprocessor macro with no arguments, and one with zero arguments
Is there any reason to prefer
#define MY_MACRO() ..stuff..
to
#define MY_MACRO ..stuff..
Don't use macros is not a valid answer...
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votes
8
answers
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views
What can you do with Lisp macros that you can't do with first-class functions?
I think I understand Lisp macros and their role in the compilation phase.
But in Python, you can pass a function into another function
def f(filename, g):
try:
...
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36
votes
5
answers
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Implicit declaration of function - C99
I am currently using Xcode 4, and in my .pch file I have this macro:
#define localize(s) NSLocalizedString((s), nil).
When I try to use this macro in some .m file, I receive this warning: Implicit ...
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How and When to Use @async and @sync in Julia
I have read the documentation for the @async and @sync macros but still cannot figure out how and when to use them, nor can I find many resources or examples for them elsewhere on the internet.
My ...
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8
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How to save a Vim macro that contains "Escape" key presses?
I use the following Vim macro a lot (it puts the current line inside XML tags):
I<e>^[A</e>
So I saved it into my .vimrc
let @e='I<e>^[A</e>'
But it does not work.
The ^[ ...
- 59.4k
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votes
2
answers
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Can javascript simulate a button click?
I am designing a site where it would be problematic if macros were allowed to run freely.
I have thought of a way to stop a macro made by simulating the HTTP requests from a button click but this ...
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votes
4
answers
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What do __STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS mean?
I see this in the standard C++ libraries for my system, as well as some of the headers in a library I'm using.
What are the semantics of these two definitions? Is there a good reference for #defines ...
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13
answers
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What useful macros have you created in Netbeans? [closed]
I use Netbeans (nightly build) for Ruby on Rails development and I'm looking to beef up my macros. I've created a few myself:
copy identifier:
select-identifier copy-to-clipboard
paste clipboard ...
- 4,908
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votes
2
answers
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views
Scala macros and the JVM's method size limit
I'm replacing some code generation components in a Java program with Scala macros, and am running into the Java Virtual Machine's limit on the size of the generated byte code for individual methods (...
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votes
9
answers
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How do I implement no-op macro (or template) in C++?
How do I implement no-op macro in C++?
#include <iostream>
#ifdef NOOP
#define conditional_noop(x) what goes here?
#else
#define conditional_noop(x) std::cout <&...
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how to find the source of some macros
There are many places for defining a macro.When the macro is defined in our own project by us,the are easy to find the definition position for them.
But when i try to learn some famous open source ...
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8
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Examples of what Lisp's macros can be used for
I've heard that Lisp's macro system is very powerful. However, I find it difficult to find some practical examples of what they can be used for; things that would be difficult to achieve without them.
...
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2
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What is the __STDC_VERSION__ value for C11?
I know that compilers use __STDC__ to indicate that a compiler is standard C and, from, there, you can use __STDC_VERSION__ to figure out which level of the standard you're using.
I also know that ...
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3
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Does Q_UNUSED have any side effects?
Given the following piece of code:
void test(int var)
{
Q_UNUSED(var);
#ifdef SOMETHING
printf("%d",var);
//do something else with var...
#endif
}
Would the Q_UNUSED macro have any ...
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votes
1
answer
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Mathematica: Unevaluated vs Defer vs Hold vs HoldForm vs HoldAllComplete vs etc etc
I'm bewildered by all the built-in Mathematica functions that purport to prevent evaluation in some way: Unevaluated, Defer, Hold, and over half a dozen of the form Hold*. The Mathematica ...
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votes
6
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Implement generic swap macro in C [duplicate]
Possible Duplicate:
is there an equivalent of std::swap() in c
Hi folks,
I was attempting a problem to write a generic swap macro in C and my macro looks like this:
#define swap(x,y) { x = x + ...
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votes
7
answers
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Macros to create strings in C
Alternative titles (to aid search)
Convert a preprocessor token to a string
How can I make a char string from a C macro's value?
Original Question
I would like to use C #define to build literal ...
- 25.7k
33
votes
7
answers
21k
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C++ - enum vs. const vs. #define
At the end of the article here: http://www.learncpp.com/cpp-tutorial/45-enumerated-types/, it mentions the following:
Finally, as with constant variables, enumerated types show up in the debugger, ...
- 48.2k
33
votes
3
answers
21k
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How do I match the type of an expression in a Rust macro?
This is just pseudocode:
macro_rules! attribute {
$e: expr<f32> => { /* magical float stuff */ };
$e: expr<i64> => { /* mystical int stuff */ };
};
I would like to have a ...
- 8,177
33
votes
4
answers
11k
views
Is it possible to declare variables procedurally using Rust macros?
Basically, there are two parts to this question:
Can you pass an unknown identifier to a macro in Rust?
Can you combine strings to generate new variable names in a Rust macro?
For example, something ...
- 34k
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votes
18
answers
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The most useful user-made C-macros (in GCC, also C99)? [closed]
What C macro is in your opinion is the most useful? I have found the following one, which I use to do vector arithmetic in C:
#define v3_op_v3(x, op, y, z) {z[0]=x[0] op y[0]; \
...
- 29.9k
32
votes
7
answers
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How to repeat some action certain times on Vim?
In Vim, I usually want to repeat some series of commands some times. Say, I want to comment 5 lines, I would use
I//<Esc>j
.j.j.j.j
Is there any way to repeat the last ".j" part several times?
- 9,355