C ++中的if语句

Question

So I have been writing in c++ for a few weeks now and can't help but feel that I am using too many if statements in my code. I am aware of while, do while, and for loops but when given the scenario I always use if statements. I guess I am not exactly aware of how I could use a different method. I just finished a project and there are if statements everywhere. Could one of you guys please explain to me how I can change some of these if statements into something different but still functional? I am really just looking for guidance in the right direction. Any help will be appreciated. Thank you guys!

If statement #1 that bugs me:

    if (x >= 1)
    {
        setx_Position(3);
        sety_Position(500);
        cout << "Soldier moves: " <<getx_Position()<<", "<<gety_Position()<< "   ";
        cout << endl;
    }
    else
    {
        cout << "Soldier moves: " <<getx_Position()<<", "<<gety_Position()<< "   ";
        cout << endl;
    }
    return 0;

Second if statement bugging me is :

    a--;
    if (a >= 0)
    {
        cout << "Soldier fires weapon : Pistol " << "(" << a << " bullets left)" << endl;
    }
    else if (x <= 0)
    {
        cout << "Soldier fires weapon : NO WEAPON FIRED! (DEAD)" << endl;
    }
    return 0;

Both of these just feel lengthy and unnecessary to me. How could I get the same results with a much cleaner look? Or is this the best way to do it?

Answer 1

There's nothing wrong with having to use if statements, they're often a must when you need to perform an action conditionally. As for improving your snippets, an obvious thing to do in the first one is to move the common sections of code outside the if-else block.

if (x >= 1)
{
    setx_Position(3);
    sety_Position(500);
}
cout << "Soldier moves: " << getx_Position() << ", " << gety_Position() << "   ";
cout << endl;

The second one looks pretty good as is. The only thing I see that could (arguably) be an improvement is to remove a--; and change the if condition to if(--a >= 0)

Answer 2

好吧，图灵会为忠于原始图灵机的行为而感到自豪，但是在现代C ++中，您的武器库中还有其他武器，我建议您读一本有关模式的书，也许这本书中没有“优化”或从片段中提出一些建议，这是没有意义的，因为如果不能真正影响您的生产技能，那么您就需要有关高级C ++技术的基础。

Answer 3

well an if statement is a very common thing to use in code, especially in logic heavy sections, such as game code.

in c++ one way to avoid lots of if blocks for different things is to use Polymorphism, or function pointers.

switch statements can also be good.

I can't really see any better way of doing your two examples, except for the optimization of example one mentioned by Praetorian

Answer 4

A great deal depends upon what sort of logic you're willing to use to avoid an if statement.

For example, let's consider your second example. You really have pretty much the same actions in both legs of the if statement -- you mostly just supply different data to write to the output. If you don't mind some minor changes in wording, it's pretty easy to eliminate the if statement entirely:

static char const *prefixes[] = {
    "Soldier tries to fire (but has ",
    "Soldier fires Weapon: Pistol ("
};

std::cout << prefixes[--a >= 0] << a << " bullets left)\n";

It's a little hard to say whether I'd recommend this or not. At first glance, the code is obviously a lot simpler and cleaner -- no conditions or if statements to deal with at all. At the same time, for somebody who's unaccustomed to this style, it would undoubtedly lead to some serious head-scratching.

Answer 5

please explain to me how I can change some of these if statements into something different but still functional?

If you need to make decisions, you need if statements. Thing is, if you have many many of them littering the code I agree with you that you would want to think long and hard about how to make the code more readable by performing the logic in other ways. (Remember, (paraphrasing) code is mainly for reading; and only occasionally for the computer to execute). You probably don't want code that is too 'procedural', ie one long stream of C-like code. Create classes/objects that react to your simulation, thus encapsulating much of the logic. And please, don't have massively nested if/else spaghetti.

Another reason to reduce the number of if's is that if blocks are the most likely parts of your code to contain bugs, and are the hardest to test. (You are writing tests, right?)

But as others have said, there's not enough context. Oh, and name your variables like "NumBulletsRemaining" instead of x or whatever :)