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We need to talk about nested functions, let's say you have a function like this called Two Steps Forward,



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one back, and we pass in a distance of steps, which then returns an integer.



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And what this function is going to do is take literally two steps forwards and then one back multiplied



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by the distance that you pass in.



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Okay.



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And if you're not from the English speaking world, perhaps you don't recognize this, but it's a common



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I don't know, it's in common parlance, in common English.



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Sometimes things are so hard in life.



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You take two steps forwards, but you always slide one back.



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And I put coding in that category.



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When you're just learning, it's pretty difficult to learn it.



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Right.



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How would we do this?



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Well, most people would type a line of code, a line of code, a line of code, etc..



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OK, but what we can do is we can nest functions so we can declare a function inside of a function.



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And I've got a couple here.



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This is the forward one, so we have a function forward which goes a distance and passes and passes



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out an integer.



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Now this is all mashed together in one line.



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We can actually do this.



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So for Swift, it doesn't actually matter if you're all in one line or not, because it'll evaluate



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the same way, other languages don't necessarily do that.



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So be careful in that respect.



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It's what this function forward does is return the distance times to because two steps forwards, then



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we have a function for backwards.



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Can you guys hear that plane outside?



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Because I sure can it's really loud to me, but you probably can't hear it.



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OK, then we have a function for backward which returns the distance times minus one, because two forwards,



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one backwards.



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Backwards is negative.



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Now, I cannot call those functions outside of the original function, so I can't say forward.



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It just doesn't exist.



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Same for backward, nothing that.



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But I can actually call them inside here.



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And I can pass in the distance, I can also call backward.



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Pass in the distance.



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So we want to have forward and backward and what have I got here?



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Yes, we're going to add them.



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So put this onto the next line at that, and then we're going to return it.



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So if we run that function.



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With two, we should get an answer of two, because it'll go four steps forward and two back against



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to.



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And there's the answer we have to now, obviously, the way the maths of this works out is we just simply



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get back, I think the number that we originally put in.



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So it's for.



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That's just the way the math works out, but my point is a nested function sits inside a function.



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Now, you're going to come across this concept quite often, but it won't necessarily have the function



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keyword attached to it.



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What you have to recognize is when you have these curly braces and that tells you that what you're looking



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at is a function, whether it's named or it's anonymous doesn't matter.



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You're looking at a nested function.



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I tend not to use nested functions, to be honest, I don't think they're very useful in terms of structuring



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your code and they might confuse things.



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But as always, there are use cases for everything.



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Right.



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Time for you to do the same thing.



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Here's your homework and make a function to add two numbers.



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Use a nested function to check.



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The answer is less than 10 and return greater than if it is.



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That should be less than it.



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And return less than if it is less than 10 or greater than 10, if it's not less than 10, right.



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So a lot of confusing words there, I think even now that I've done it.



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But I'm saying it I feel pretty confused reading it and see what you can make of that and let me see



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what you come up with.