Project Title

About
Concepts

About

💾 Prototype

	int ft_printf(const char *str, ...);

⚙️ Parameters

const char *str: The string to be printed
...: arbitrary number of arguments

◀️ Return value

Returns an integer that represents the number of characters in the printed string

Must recode the libc's printf function and it will be compared to real one
It must not do the buffer management like the real printf
Must use the command ar to create the library (libtool is forbidden)
Libft library is allowed

Must manage the following conversions: cspdiuxX%

%c prints a single character

%s prints a string of characters

%p the void * pointer argument is printed in hexadecimal

%d prints a decimal (base 10) number

%i prints an integer in base 10

%u prints an unsigned decimal (base 10) number

%x prints a number in hexadecimal (base 16) - lowercase

%X prints a number in hexadecimal (base 16) - uppercase

%% prints a percentage sign

Concepts

Variadic functions

This project calls for using a new standard C library → <stdarg.h>

This library is used to allow functions to accept an indefinite number of arguments. It facilitates stepping through a list of function arguments of unknown number and type.

Stdarg has one type:

va_list: type for iterating arguments

Stdarg Macros:

va_start: start iterating arguments with a va_list. va_start expects a va_list & the last required argument
va_arg: retrieve an argument. Expects a va_list & data type as input. Type must be self-promoting (no chars, shorts or floats).
va_end: free a va_list
va_copy: copy contents of one va_list to another

Code Example

#include <stdarg.h>
#include <stdio.h>
 
// this function will take the number of values to average
// followed by all of the numbers to average
double average ( int num, ... )
{
    va_list arguments;                     
    double sum = 0;
 
    // Initializing arguments to store all values after num. 
		// Va_starts expects a va_list & last required argument
    va_start ( arguments, num );           
    // Sum all the inputs; we still rely on the function
    // caller to tell us how * many there are
    for ( int x = 0; x < num; x++ )        
    {
        sum += va_arg ( arguments, double ); 
    } // va_arg expects va_list & data type
    va_end ( arguments );   // Cleans up the list
 
    return sum / num;                    
}
 
int main()
{
    // this computes the average of 13.2, 22.3 and 4.5 (3 indicates the number of values to average)
    printf( "%f\n", average ( 3, 12.2, 22.3, 4.5 ) );
    // here it computes the average of the 5 values 3.3, 2.2, 1.1, 5.5 and 3.3
    printf( "%f\n", average ( 5, 3.3, 2.2, 1.1, 5.5, 3.3 ) );

Example by Allain

sdnc/ft_printf