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In C# what is the difference between myint++ and ++myint?

Hopefully this is not too general or weird of a question. Also, couldn’t find it on Google, don’t whether this is just too dumb of a question or whether I fail at Google.

So, I forget where I read this from but, it said that using ‘++x’ (or whatever other variable) is somehow more optimized or whatever you might call this than, ‘x++’.

So, is this just a looks thing or is one truly faster? Like, they do the exact same thing so, that is why I am asking.

Answer 1

They’re doing different things. The first is pre-increment, and the second is post-increment. If you use either alone on a line, you won’t notice the difference. But if you do (for instance):

a = x++

or

a = ++x

you will. With post-increment, you get the value, then increment. With pre-increment, you increment, then get the value. See http://en.wikipedia.org/wiki/++#Use_in_programming_languages for a brief explanation (they use JS as an example, but it applies equally to C#)

EDIT: By popular demand (and to refute a couple exaggerations), here’s a little about performance with primitives in C++. Take this example program:

int main()
{
    int a;
    int x = 14, y = 19;
    a = x++;    
    a = ++y;    
}

It compiles (g++, just -S) to the below on x86. I have removed irrelevant lines. Let’s look at what’s happening and see if unnecessary duplicates are being made.:

        # Obvious initialization.
        movl    $14, -12(%ebp) 
        movl    $19, -16(%ebp)

        movl    -12(%ebp), %eax # This is moving "old x" to the accumulator.
        movl    %eax, -8(%ebp) # Moving accumulator to a.
        addl    $1, -12(%ebp) # Increment x (post-increment).

        addl    $1, -16(%ebp) # Increment y (pre-increment)
        movl    -16(%ebp), %eax # Move "new y" to accumulator.
        movl    %eax, -8(%ebp) # Move accumulator to a.

We’re done.

As you can see, in this example, the exact same operations are required in each case. Exactly 2 movl, and 1 addl. The only difference is the order (surprised?). I think this is fairly typical of examples where the increment statement’s value is used at all.