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Symbolic Constant

Each #define line consists of three parts:

The body of a macro can be not only a single numeric value, but also other macros or entire expressions:

c

main

copy

              
12345678910

            
#include <stdio.h>
#define TWO 2                                // macros with value.
#define RESULT TWO*TWO                       // TWO is replaced by the number 2.
#define PRINT printf("result = %d", RESULT);

int main() 
{
   PRINT 
   return 0;
}

Every time the compiler encounters “TWO”, it will simply substitute its value 2.

The macro is immutable. Once defined, it is a permanent textual substitution within the file or scope where it is defined.

Why do we need this? Why not just use variables?

What is better to use?:

  • If the value never changes, const is better, because it is safer;

  • If you need to substitute a simple number or text, you can use a macro.

  1. Create an object macro add, the body of the macro is an addition operator +.

  2. Use a macro to add any two numbers.

Opgave

Swipe to start coding

  1. Create an object macro add, the body of the macro is an addition operator +;
  2. Use a macro to add any two numbers.

Løsning

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book
Symbolic Constant

Each #define line consists of three parts:

The body of a macro can be not only a single numeric value, but also other macros or entire expressions:

c

main

copy

              
12345678910

            
#include <stdio.h>
#define TWO 2                                // macros with value.
#define RESULT TWO*TWO                       // TWO is replaced by the number 2.
#define PRINT printf("result = %d", RESULT);

int main() 
{
   PRINT 
   return 0;
}

Every time the compiler encounters “TWO”, it will simply substitute its value 2.

The macro is immutable. Once defined, it is a permanent textual substitution within the file or scope where it is defined.

Why do we need this? Why not just use variables?

What is better to use?:

  • If the value never changes, const is better, because it is safer;

  • If you need to substitute a simple number or text, you can use a macro.

  1. Create an object macro add, the body of the macro is an addition operator +.

  2. Use a macro to add any two numbers.

Opgave

Swipe to start coding

  1. Create an object macro add, the body of the macro is an addition operator +;
  2. Use a macro to add any two numbers.

Løsning

Switch to desktopSkift til skrivebord for at øve i den virkelige verdenFortsæt der, hvor du er, med en af nedenstående muligheder
Var alt klart?

Hvordan kan vi forbedre det?

Tak for dine kommentarer!

Sektion 2. Kapitel 1
Switch to desktopSkift til skrivebord for at øve i den virkelige verdenFortsæt der, hvor du er, med en af nedenstående muligheder
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