Difference between Inline and Macro

The inline and macro functions are employed in C++ and C programming. Inline functions are more commonly utilized than macros, and a macro is an instruction that expands when it is invoked. Functions may be defined, like macros. In the same way, inline functions expand at the moment of the call. The main distinction between inline and macro functions is that inline functions are extended during compilation. In contrast, the macros are expanded when the preprocessor processes the program.

In this article, you will learn the difference between inline and macro. But before discussing the differences, you must know about inline and macro with their syntax and example.

What is the Inline Function?

An inline function is a typical function that is specified with the inline keyword. An inline function is a small function that the compiler expands, and its arguments are only considered once. Inline functions are short-length functions that are created automatically without the need for the inline keyword within the class.

Syntax of an Inline Function:

You can use the following syntax to apply the inline function:

inline return_type function_name ( parameters )
{ 
 // here, write the code for the inline function
}

Example:

Let's take an example to understand the inline function.

#include <iostream>
using namespace std;

// This is the Inline function
inline int Maxnumber(int x, int y)
{
	return (x > y) ? x : y;
}

// This is the main function of the program
int main()
{
	cout << "Max (150, 500):" << Maxnumber(150, 500) << endl;
	cout << "Max (30, 10): " << Maxnumber(30, 10) << endl;
	return 0;
}

Output

Max (150, 500): 500
Max (30, 10): 30

What is Macro Function?

Macros are statements or expressions that are handled prior to program compilation. This process is referred to as 'preprocessor directives'. Macros begin their declaration with a '#define'. A macro is used to offer a name to a statement or expression. Wherever the preprocessor discovers the name of a macro in the program, it replaces it with its definition. As a result, the macro is simply a 'text replacement'. Even the keywords may be specified as macros because the compiler identifies them, not the preprocessor.

Syntax of Macro Function:

You can use the following syntax to apply the macro function:

Example:

Let's take an example to understand the macro function.

#include <iostream>
using namespace std;
  
// macro with a parameter
#define MAXNUMBER(a, b) (a > b) ? a : b
  
// Main function of the program
int main()
{
    cout << "Max (150, 1800): ";
    int k = MAXNUMBER(150, 1800);
    cout << k << endl;
  
    cout << "Max (35, 15): ";
    int k1 = MAXNUMBER(35, 15);
    cout << k1;
  
    return 0;
}

Output

Max (150, 1800): 1800
Max (35, 15): 35

Key differences between Inline and Macro function

There are various key differences between inline and macro functions. Some of the key differences between inline and macro functions are as follows:

The macros are expanded by the preprocessor. In contrast, the compiler copies the inline function at the place of calling.
The arguments provided to inline functions are only evaluated once during compilation. In contrast, the macro's arguments are assessed every time when a macro is utilized in the code.
In the inline function, debugging is very easy because they are checked for errors during compilation. On the other hand, debugging is difficult in the macro function because a macro is not checked during compilation.
The term "inline" is utilized to define an inline function. In contrast, the keyword "#define" is utilized to define a macro.
Macros are often single-line declarations that are followed by a new line. In contrast, the declaration of inline functions is ended by '}' just like normal functions.
The short functions defined within a class without the inline keyword are automatically made inline functions. In contrast, the macro function should be defined precisely.
As a function, an inline function binds its members within opening and closing curly braces. In contrast, macro functions lack a termination symbol, so binding becomes tricky when the macro has more than one statement.
Inline functions have access to the class's members. On the other hand, a macro may never access the class's members.
In the inline function, the compiler may not be able to inline and expand all of the functions declared within a class. In contrast, the macros functions are always expanded.
A closing curly brace is necessary to end an inline function. In contrast, a macro function ends with the start of a new line.
The inline function is not utilized in competitive programming. In contrast, the macro function is utilized in competitive programming.

Head-to-head comparison between Inline and Macro function

Here, you will learn the head-to-head comparisons between inline and macro functions. The main differences between inline and macro functions are as follows:

Features	Inline function	Macro Function
Definition	An inline function is a C++ improvement feature that reduces program execution time.	A macro is a preprocessor directive that is included at the beginning of the program and preceded by a hash sign.
Syntax	The syntax of the inline function is: inline return_type funct_name ( parameters ){ . . . }	The syntax of the macro function is : #define macro_name char_sequence
Keyword	It is defined by the inline keyword.	It is defined by the #define keyword.
Evaluation	It evaluates the argument only once.	It evaluates the argument every time when it is utilized in the code.
Usage	An inline function may be utilized to reduce program execution time.	It may be utilized to specify constants, functions, expressions, literal text substitution, and other things.
Accessing	It may access the data of members of the class.	Macros can never be class members and may not access the class's data members.
Defined	It may be specified inside or outside the class.	It may be specified at the start of the program.
Expansion	In the inline function, the compiler may not be able to inline and expand all of the functions declared within a class.	It is always expanded.
Termination	It terminates with the curly brackets at the end of the inline function.	It terminates with the start of the new line.
Automation	The short functions defined within a class without the inline keyword are automatically made inline functions.	The macro function should be defined precisely.
Debugging	In the inline function, debugging is very easy because they are checked for errors during compilation.	Debugging is difficult in the macro function because a macro is not checked during compilation.
Binding	As a function, it binds its members within opening and closing curly braces.	Macro functions lack a termination symbol, so binding becomes tricky when the macro has more than one statement.

Conclusion

This article explained the distinction between Inline and Macro Functions. Both of these concepts are employed in C++ programming. The main distinction between macros and inline functions is that macros are verified by the preprocessor, whereas the compiler checks inline functions. Inline functions are significantly more convincing than macro functions. C++ also has a better approach to defining a constant, which uses the "const" keyword

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