Unreal Development Kit Game Programming with UnrealScript：Beginner's Guide

上QQ阅读APP看书，第一时间看更新

Time for action – Using logical operators

Let's put our first example in code.
```
var bool bRaining;
var float CurrentMoney, RequiredMoney;

function PostBeginPlay()
{
    'log(!bRaining && CurrentMoney > RequiredMoney);
}

defaultproperties
{
    CurrentMoney=20.0
    RequiredMoney=15.0
}
```
Remembering that bools are false by default, let's take a look at the log:
```
[0007.94] ScriptLog: True
```
Even though bRaining is False, we're asking the code if it's NOT raining, which is True. You can see why naming booleans is important now. If our variable were called bNotRaining , working with logical operators would get messy pretty quickly.

Let's look at our second example.

var string Day;

function PostBeginPlay()
{
    'log(Day == "Tuesday" || Day == "Thursday");
}

defaultproperties
{
    Day="Monday"
}

Since the day variable is neither of those two, we'll get False in the log:

[0007.79] ScriptLog: False

One final operator to discuss is the EXCLUSIVE OR, denoted by two carets ( ^^ ). This will return true if one and only one of our statements is true. Let's look at the following code:
```
var string Day, Month;

function PostBeginPlay()
{
    'log(Day == "Tuesday" ^^ Month == "January");
}

defaultproperties
{
    Day="Tuesday"
    Month="January"
}
```
If we were using a normal OR, this would return true, but since both of them are true, an EXCLUSIVE OR returns false:
```
[0007.60] ScriptLog: False
```

What just happened?

We can see how intertwined logical operators are with normal comparisons. We used the equal and greater than comparisons in our examples. When working with them, the best way to figure out how to write a statement is to say it out loud first and take note of words like AND, NOT, and OR in your sentence. This will help you figure out how to construct a logical operator statement.

Have a go hero – Writing logical statements

How would you write the following statement with logical operators?

If the sun is shining and we're not wearing sunblock...…

Answer: The operator would look something like this:

if(bSunShining && !bWearingSunblock)

Concatenation

Concatenation is a fancy word for "join two strings together". There are two concatenation operators, let's take a look at them.