CODEWITHSUNDEEP
cfor-loop
Abdaal Ahmad
Abdaal Ahmad

Reputation: 27

for loop is initialising with three variables

I have a doubt that why 3 variables wstart = wend = start; are used to initialise the loop.if the value of any of these variable changes will it change the value of both variable ???

void reverseletter(char str[], int start, int end) {               
    int wstart, wend; 
    for (wstart = wend = start; wend < end; wend++) { 

        if (str[wend] == ' ') 
            continue; 

        // Checking the number of words 
        // present in string to reverse 
        while (str[wend] != ' ' && wend <= end) 
            wend++; 
        wend--; 

        //Reverse the letter 
        //of the words 
        reverse(str, wstart, wend); 
    } 
}

Upvotes: 0

Views: 76

Answers (4)

Jabberwocky
Jabberwocky

Reputation: 50776

An assignement like b = c is itself an expression whose value is the value of b after the assignment.

Therefore

a = b = c;

can be seen as

a = (b = c);

which is equivalent to:

b = c;
a = b;

All three variables a,b and c stay totally independent of each other.

You can demonstrate this with following snippet:

int a = 1;
int b = 2;
printf("%d\n", a);
printf("%d\n", a = b);
printf("%d\n", a);

Output

1
2
2

Upvotes: 1

Spikatrix
Spikatrix

Reputation: 20244

wstart = wend = start is the same as

wend = start;
wstart = start;

if the value of any of these variable changes will it change the value of both variable ?

No, changing one variable won't affect the others, all 3 are independent variables.

Upvotes: 3

JeremyP
JeremyP

Reputation: 86651

This snippet

wstart = wend = start

takes advantage of the fact that, in C, assignment is an expression that returns a value. What happens is that wend = start assigns the value of start to wend and "returns" it. This "return" value is assigned to wstart. Thus the overall effect is to assign start to both wend and wstart.

It's a style I've seen before but I don't personally like it. I would prefer:

for (wstart = start, wend = start; wend < end; wend++)

which does the same thing but in a clearer way IMO.

Upvotes: 0

Jay
Jay

Reputation: 24895

If you change one of the variables, it will not change the other. All of them do not reference to the same memory location.

int wstart, wend; 
for (wstart = wend = start; wend < end; wend++) {

wstart, wend and start, each will have their copy of the values and changing one will not change others.

Upvotes: 0

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