All language subtitles for 3. GDScript Intro Flow Control

Now that we can store data and manipulate values, we need to discuss about code execution. And the code
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executes from top to bottom without stopping.
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Of course, an algorithm cannot be created just by lines of code written without any flow control.
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This is why in this section we will be discussing about flow control instructions. And they're very
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important because otherwise nothing will be possible with programming.
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So let's find out some flow control instructions.
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Firstly, we need to discuss the IF instruction because this one is the most common. And IF is very simple,
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you just use the operator IF and then a statement that needs to resolve in either true or false.
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In this case, I'm using the operator double equals (==), which actually compares.
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It doesn't assign it compares the value from "a" with 1.
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And since this is actually true, this will return true.
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So in this case, if we'll go through the first section which will execute this part of the code, if
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"a" wasn't equal with 1, then it would have went to the else branch and it would execute that part
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of the code.
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Keep in mind that the else branch is optional so it can be completely removed if not necessary.
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For example, a code can be just if "a" == 1 do something.
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If not, then I don't care about that part of the code.
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Now let's look at another important function which is similar with IF but has something particular.
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This one is called the MATCH instruction.
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And in other programming languages you might be familiar with the instruction SWITCH because it's very
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similar.
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So the main difference between an IF statement and the MATCH statement is the fact that in a IF statement
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we can have a statement made out of multiple instructions.
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Well, here in MATCH we have a variable, let's say "a", and then if that variable has multiple numbers
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or strings that can be, then it's much easier to write this.
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Keep in mind that with IF we can actually implement a MATCH instruction, but with a MATCH, we
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cannot really implement a complete IF instruction. In some cases, for example, in this one we can,
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but in some others we cannot.
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Let's quickly look at how we can implement this MATCH with an IF.
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If "a" == 1, then.
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Print is one.
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And then there is another instruction called else if (ELIF) it's basically else and if combined and "a" == 2
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print is 2.
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We could have opted for this implementation.
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But as you can see, if we add more values here like three, four, etc., then the MATCH is much more
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pleasant for the eye to parse rather than using an IF statement.
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So you might be considering what to use based on what values you are comparing.
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While the IF instruction and the MATCH instruction actually branch out the code, we have other types
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of flow control which actually deal with looping code.
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And the most common one is the FOR instruction. And the FOR instruction works like this:
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We have a value and we can give it a range, a list and some other things to iterate. Also FOR might
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be called the iteration operator because what it does, it goes through a list of values and parses
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each one of them.
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So if we were to run this, it will print zero, one, two, three, four.
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Let's see.
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So for the FOR instruction, we have zero one, two, three, four, because it starts from zero.
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And of course, it needs to be lower than five to actually finish.
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One pro of the FOR instruction is the fact that we can iterate lists like the one described in the previous
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example and also ranges.
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So for example, counting and so on, so forth.
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One disadvantage for the FOR instruction is the fact that we cannot parse values that we cannot count.
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And for this we can use the WHILE instruction.
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The WHILE and FOR are very similar in a lot of cases because they both loop code, they both work in
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similar ways because they test the condition to loop another time.
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But one major difference is the fact that the FOR knows exactly how many steps it needs to take and
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the WHILE doesn't.
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In this example, we can clearly see what that means.
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For example, we have the HP of the player and then we will subtract different values.
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In fact, random values from that.
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HP until it reaches zero.
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This might be, for example, while health is more than zero, but we don't know exactly how much because
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in this range we actually subtract from 10 to 30 points.
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And then by just running this, we can see that sometimes this happens with less steps and some
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other times if more steps. Let's quickly try it.
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So I'm going to press F6.
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So in this case.
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We started with 100.
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And then the health decreased.
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And then we ended up with seven steps.
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Let's run it again.
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Now it seems that the random did a better job, so we ended up with six steps.
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This could not have been implemented with a FOR.
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Now let's look at functions.