Why (long)NULL ?

From: sugaray (ruicui_at_sohu.com)
Date: 02/29/04 

Date: 28 Feb 2004 22:30:15 -0800

Hi, I just came upon this code snippet which parses a string stored in buf
with comma(,) as delimiter and store each substring into args, the question
I'm having here is that I don't get why in the first while-statement the OP
cast the NULL to a (long), isn't *buf a char ? and another question is what's
the purpose of NULL in string manipulation, and how to test to see if an input
string is empty ? Thanx for your help.

void parse (char *buf, char **args) {
        
        while (*buf != (long) NULL ) {
                                
                while ( *buf == ',' )
                         *buf++ = (long) NULL ;
                        
                *args++ = buf;
                                        
                while ( (*buf != (long) NULL) && (*buf != ',') )
                          buf++;
                
                }
        *args = NULL;
        
        }

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