do-while

Question

Hi! Why does the increment a ++ and ++ a of the example below make no difference in the program?
int a = 0;
do {
Console.WriteLine(a);
a++;
} while(a < 5);

/* Outputs
0
1
2
3
4
*/

Thank you!

Answer 1

because they both do the same thing in this context

Answer 2

Because it's in its own statement.
a++ first uses then increments.

So, look at the statement:
a++.
First use.
Ok, well we're not really using it for anything except incrementing it anyway.
Increment, ok now a = a +1.

Now look at
++a.
First increment.
Ok, now a = a +1;
Now use.
Ok, well we aren't really using it. Just assigning a.

I don't get the source of your confusion.
Did you mean to ask:
Console.WriteLine(++a);
Or
Console.WriteLine(a++);
??
Because that will surely give different results, as the ++a one will increment first. So the first result would be 1.

Answer 3

@Limitless. does prefix/postfix work like that in c#. I was under the impression that var++ increments after the statement/expression is evaluated. Not wait until next time it is encountered.

Answer 4

thought so, i wasnt sure about in c# either thus the question. I am sure that is how it works in c++ though.

Answer 5

So try putting the a++ and ++a in your Console.WriteLine()

You'll get 1..5 and 0..4
Now why is this?

If you look at the rules of the ++ function you'll know that the a variable will increase immediately when it's ++a and when it's a++ it will only increase once it's used again.

Now the reason why it didn't matter in your code was because when the a variable got to While(a < 5) the value would the same in both cases.

if you wanted it to be different I would suggest something like While(a++ < 5)
That will make it loop one more time ;)

Answer 6

here in this context a++; is terminated there..
but if it would be have been like
considering
int a=5;
b=a++; // output will be b=5, and a=6
and one more expression
c=++a; // Output will be c=6 and now a=7

Answer 7

"i++ means 'tell me the value of i, then increment'

++i means 'increment i, then tell me the value'"

Safe to say you're right

Answer 8

Now I understand. What was making me confused was the line "console.WriteLine (a);"
But changing this line to "console.WriteLine (a ++)" or "console.WriteLine (++ a)" is easier to understand.
Here's how the two exits are:

int a = 0;
do
{
Console.WriteLine(++a);
} while(a < 5);
/* Outputs
1
2
3
4
5
*/

int a = 0;
do
{
Console.WriteLine(a++);
} while(a < 5);
/* Outputs
0
1
2
3
4
*/

The line "console.WriteLine (a)" forced the program to start "a" always at 0.

Anyway, thank you for the help.

Answer 9

Ok maybe it's changed after it's been used.

Not sure about that