59 lines
1.5 KiB
Markdown
59 lines
1.5 KiB
Markdown
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---
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title: Macros in C
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---
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## Macros in C
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A macro is a piece of code with a given name. When the name is used, it is replaced by the content of the macro.
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#### Defining macros
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The `#define` keyword is used to define new macros. It's followed by a name and a content. By convention, macro names are written in uppercase.
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```C
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#define PI 3.14
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```
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If you use the macro this way:
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```C
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printf("Value of PI: %d", PI);
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```
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Is the same as write this:
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```C
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printf("Value of PI: %d", 3.14);
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```
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#### Types of macros
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There are two type of macros. The `Object-like` macros, showed above, and the `Function-like` macros.
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#### Function-like Macros
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Function-like uses the same `#define` keyword. The difference is that you use a pair o parentheses after the function name.
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```C
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#define hello_world() printf("Hello World!")
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```
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So calling:
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```C
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hello_world()
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```
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You get:
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```C
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printf("Hello World!");
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```
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You can set parameters too:
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```C
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#define hello(X) printf("Hello " X "!")
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```
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Now calling:
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```C
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hello("World");
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```
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You get the equivallent of:
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```C
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printf("Hello World!");
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```
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#### More Information:
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<!-- Please add any articles you think might be helpful to read before writing the article -->
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[GCC Online Documentation: Macros](https://gcc.gnu.org/onlinedocs/cpp/Macros.html)
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[GCC Online Documentation: Object-like macros](https://gcc.gnu.org/onlinedocs/cpp/Object-like-Macros.html#Object-like-Macros)
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[GCC Online Documentation: Function-like macros](https://gcc.gnu.org/onlinedocs/cpp/Function-like-Macros.html#Function-like-Macros)
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