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What does the following C statement do?
while(*c++ = *d++); assuming c and d are pointers to characters.5,273 Views |
(13 votes, avg: 3)
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What does the following C statement do?
while(*c++ = *d++); assuming c and d are pointers to characters.
5,273 Views | (13 votes, avg: 3)
Loading ...
The loop will be executed until d reaches a null character
string copy
string copy utill zero appears
String copy is performed indeed but be careful with the space allocated for the destination string.
Check this example:
char s1[10]=”abcde”;
char s2[3];
char* c,*d;
c=s2;
d=s1;
while(*c++ = *d++);
printf(”%s - %sn”,s1,s2);
The code is string copy. But it does not add a null pointer to the end. There should also be a check for overlapping addresses.
Where is a logical value being returned in the while(*c++ = *d ++)
*c++ = *d++ is not a logical expression, hence incorrect syntactically.
Isn’t it. Please correct me if i’m wrong.
String copy–for sure
All that the basic operation :
while (*c++ = *d++)
;
does is to copy the destination string’s characters to the source string (here ‘d’ to ‘c’). In the above statement, one after another, the contents being pointed to by the destination pointer (’d') are faithfully copied into the source string, pointed to by (’c').
Then the while condition is evaluated, which works on a boolean basis (TRUTH/FALSITY). In C, a true value is non-zero and false value is ‘0′.
So, until the source string (’d') hits the end of the string, ‘ ’ (ASCII - 0), all the contents are copied into the string pointed to by (’c'), including the string delimiter ‘ ’, and evaluated by the while finally for truth/falsity.
The above is a short form of writing :
while (*c == *d) {
c++;
d++;
}
jobhunter:
*c++ = *d++
evaluates to the char that was assigned to *c. This is the “boolean” value that while tests. So if this char is 0, then while fails; else it continues.
it’s a string copy function.
after assignment of null char to destination string only while loop fails.care should taken on the size of destination string.
char pointers initiated as a string is read only,U cannot write anything on that.so if c is declared as a type char *c=”hello”,
then *c++=*d++ will not work.
This would either crash or would be an infinite loop because there is no breaking condition. So it doesn’t matter what c or d were.
I think that since no termination condition is given so it will go in a infinite loop no matter what s &d contains
The piece of code will not go in an endless loop.For ex: consider
char str1[10] = “ABCDE”;
char str2[10] = “FGHIJ”;
char * c = str1;
char *d = str2;
while(*c++ = *d++);
printf(”%s…%s\n”,s1,s2);
Output will be FGHIJ…FGHIJ
why because the condition copies each character one by one untilthe pointer encounters a NULL character in the array and as it is shown the character array str1 and str2 is of size 10 each and only 4 indexes are used (starting from 0) meaning remaining index values are considered as NULL. So the loop does terminate.
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