An Implementation Of Itoa

[bennyone]

the following implementation i found on the internet on a reliable source have to work
i don't understand a specific row 21 how do you write a string with [ brackets and what does it mean?

1.	/**                                                                                                                                                          
2.	 * C++ version 0.4 char* style "itoa":                                                                                                                       
3.	 * Written by Lukás Chmela                                                                                                                                   
4.	 * Released under GPLv3.                                                                                                                                     
5.	*/
6.	 
7.	char* itoa_c(int value, char* result, int base)                                                                                                          
8.	{                                                                                                                                                        
9.	    // check that the base if valid                                                                                                                      
10.	    if ( base < 2 || base > 36 ) {                                                                                                                       
11.		*result = '\0';                                                                                                                                  
12.		return result;                                                                                                                                   
13.	    }                                                                                                                                                    
14.	 
15.	    char* ptr = result, *ptr1 = result, tmp_char;                                                                                                        
16.	    int tmp_value;                                                                                                                                       
17.	 
18.	    do {                                                                                                                                                 
19.		tmp_value = value;                                                                                                                               
20.		value /= base;                                                                                                                                   
21.		*ptr++ = "zyxwvutsrqponmlkjihgfedcba9876543210123456789abcdefghijklmnopqrstuvwxyz"[35 + (tmp_value - value * base)];                             
22.	    } while ( value );                                                                                                                                   
23.	 
24.	    // Apply negative sign                                                                                                                               
25.	    if ( tmp_value < 0 )                                                                                                                                 
26.		*ptr++ = '-';                                                                                                                                    
27.	    *ptr-- = '\0';                                                                                                                                       
28.	 
29.	    while ( ptr1 < ptr ) {                                                                                                                               
30.		tmp_char = *ptr;                                                                                                                                 
31.		*ptr-- = *ptr1;                                                                                                                                  
32.		*ptr1++ = tmp_char;                                                                                                                              
33.	    }                                                                                                                                                    
34.	 
35.	    return result;                                                                                                                                       
36.	}


  

[Peter87]

The string literal "zyx..." is an array of characters. Like with any other array you can access elements by putting an index inside [ ].

array [ index ]

[bennyone]

and *ptr++ = ponits to a sepcific character and then make one addition of the pointer ?

[Peter87]

Splitting it over two lines makes it easier to follow.

*ptr = ...
ptr++;