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Okay.

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Today's lecture is going to dive deeper into the data type string.

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We're going to learn how to add strings together, how to get specific parts of a string, how to use

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escape characters and how to use the string library.

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So let's get started.

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Now we already know that a string is simply a collection of text, right?

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We can create a string using quotations such as single quotations or double quotations.

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And we can also create multi-line strings by using two brackets like this.

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However, we can also manipulate strings in many different ways, and we can do so by using the string

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library.

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A library is simply a collection of pre-written code that developers can use to complete tasks without

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having to implement the code yourself.

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Specifically, the string library is built into Lua and lets us do several things like make a string

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completely uppercase, lowercase, or split the string into multiple different sections based on a specific

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character occurrence.

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So let's go ahead and show this library in action.

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I'm going to create a variable here.

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And I'm just going to call this variable example string.

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And we can create a string of like hello world.

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And what I'm going to do is first call our print function and pass our example string.

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And that means we should expect to see Hello World get printed in the output.

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And then next what I'm going to do is I'm going to set example string.

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I'm going to override the value inside of there equal to.

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And then to access the string library we're going to type out string.

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And then we can use the dot operator to index the string library.

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And here we get to see all of the different functions available to us inside of this library.

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For example we can set a string to be all lowercase.

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We can set one to be all uppercase.

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We can reverse a string.

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We can get sub strings.

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And there's a whole bunch of other different functions inside of the string library.

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So what I'm going to do first is demonstrate the string dot lower function.

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So we'll autofill that here.

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And then we can just pass example string again.

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So it's going to grab the value of hello World.

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And it's going to make all of the characters in there lowercase.

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And then we can call our print function again and pass our example string.

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And we should expect Hello World to print here, but it should be all lowercase.

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And then once more I'm going to override the value inside of example string.

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And I'm going to set it equal to.

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And this time we're going to use the upper function.

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And then we can pass example string.

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And then we'll print out that string as well.

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So we should get all uppercase letters here.

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And then I'm also going to demonstrate the reverse function.

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So again we'll override example string and use the string dot reverse.

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And then we can pass example string once more.

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And then the last function I would like to demonstrate is the sub or sub string function.

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So we'll do example string equal to string dot sub.

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And what this does you can see the definition right here returns the sub string of s which is what we

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pass up here that starts at I which is an index and continues until J which is the second index.

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So what this means is we pass a string to it, and we basically grab a chunk out of that string and

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store it inside of a variable.

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Or that's what this function returns.

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So for example, if I wanted to extract the word world only in here I could use the string sub function

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pass where exactly the word world starts and ends.

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So for example here at the first index which would be one is h, two is E and so on.

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And then we get to W which would have its own index.

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And then the last letter here D would also have its own index.

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So what I'm going to do is I'm going to do string dot sub.

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I'm going to pass my example string.

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And I want to get a sub string of only world here.

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So we can count.

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This is one character 2345678.

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So we know that the W starts at eight.

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So we're going to pass eight here.

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And then 910 1112 it ends at 12.

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So we can pass 12 as the second argument.

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And what this function is going to do is it's going to extract the string of world and store it inside

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of our function right here.

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And before we do that, I'm also going to print our previous example when we reverse our string here.

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So now when we print we should get our default string here.

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We should get it Lowercased.

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Here we'll get it uppercase.

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This will print it reversed.

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And then last but not least this will store it as the word of world only.

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And then we can also print that out into the console to see that as well.

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And then one last thing I would like to show you is how to get the length of a string.

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And it's actually very easy to do.

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What we do is we first put a hashtag and then we can type out our string.

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And what this returns is a number that represents the exact length of the string.

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And we can go ahead and print this out in the console as well.

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So now let's go ahead and head to the test tab.

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Hit the drop down menu and press run.

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And as you can see, we get all of our different strings printed inside of the console.

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Here we get our regular string printed out.

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Hello world!

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Here we get it all completely lowercased.

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The next one is all uppercase.

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Here we have it reversed and then here.

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Oh that's right, we reversed it.

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So we actually didn't get world here.

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But instead we got a comma o l l e.

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And that's because we had the string reversed.

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So it's grabbing these last indexes instead of world.

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So if we actually wanted to grab world again we would have to reverse our string once more.

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But as you can see right here, it printed out the number five, which represents the length or the

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amount of characters inside of the string.

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As you can see, we have one, two, three, four, and five, so that number perfectly represents the

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length of the string.

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So what I'm going to do here is before we grab the substring of our example string, I'm going to reverse

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it once more.

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So example string is equal to string dot reverse and pass example string.

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And this should now store the word of world.

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So we can go ahead and hit run again.

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And there we go.

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We get our word world.

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It grabbed it from the eighth to the 11th index.

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And that function is inclusive, meaning it includes the letter that was at the eighth index, which

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was W, and it includes the letter that was at the last index, which is the letter D, and we still

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get the length of five characters.

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Perfect.

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Next, I'm going to show you how you can concatenate two strings together.

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What is concatenate?

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Well, concatenate is basically just a fancy word for adding two things together.

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If I have multiple strings, I would like to combine into a single string.

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This is where we would use concatenation.

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So what I'm going to do is I'm going to create a second string.

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I'm going to just call this variable example string two.

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And I'm going to store in there.

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It's a great day.

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And then I'm going to create a third variable.

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I'm going to call this example string three.

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And what I'm going to do is I'm going to reference my first example string, which by the time it reaches

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this point it will just be the word world.

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Because remember Lua executes code serially starting at the top and going down.

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And that's perfectly demonstrated by each of our print statements, right?

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We print out the string, we apply a change to the string, it prints that change out, and it keeps

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going down line by line, as demonstrated here in the console.

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So we'll get the word of world here.

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And then to concatenate it with this second string right here we are going to use two dots.

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So we do one and then two.

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And then we get to pass a second string which is going to be example string two.

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Now what this has done is it's joined these two strings together into a single string and stored it

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inside of this variable.

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That means we can go ahead and print out this variable inside of the console.

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And let's go ahead and see what we get.

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So now here's our two strings joined together.

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It says world.

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It's a great day.

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Now you may be seeing.

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Hey, there's no space between those two words.

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How can we fix that?

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Well, that's also very easy to do.

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We'll go back to our script.

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And what we can do is we're going to put a quotation mark here and then another one.

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So this is a new string data type right here.

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And then we're going to add another two dots.

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And then inside of the string we're just going to put a space.

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So now we are joining these three different strings together.

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And hopefully now we should have a space between these two different strings.

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So if we hit run again.

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As you can see, we now have world.

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It's a great day and there is a space between world.

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And it's.

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One last thing I would like to mention in this lecture are escape characters.

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What exactly is an escape character?

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Well, an escape character is a special character format that doesn't represent itself as a literal

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string.

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Instead, it performs a special action.

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You might not know what I mean, but I'm going to demonstrate it to you here in a moment.

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What I'm going to do is I'm going to create a new variable again, and I'm going to call this variable

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escape characters.

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And we're going to set it equal to a new string.

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And we can say something like and Bob said today was a crazy day.

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Now you might be wondering, how can we include quotations in our text when quotations denote a string

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data type?

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Right.

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We're running into a problem here where we would like to include these quotation marks, but the interpreter

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doesn't know what's going on.

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Well, that's where an escape character would come into play.

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For example, here, this escape character, which is backslash, allows us to include this quotation

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mark into the string.

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This escape character here has a very special action to omit whatever is in front of it and include

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it into the string.

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And I can do it the exact same way here as well.

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So now this quotation mark here and this quotation mark here are going to be included inside of the

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string.

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This is the role of this particular escape character.

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Another escape character is where we can print all of the text after it on a new line, and that is

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the escape character of another backslash.

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And then we pass n.

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So what this is going to do is it's going to grab all of the text after it, and it's going to print

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it on a new line, hence the n.

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So we can go ahead and print out escape characters and you'll see exactly what I mean.

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So if we hit run here.

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We actually got an error attempt to call a nil value on line 28.

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I always love errors because we get to solve them in real time.

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So if we go to line 28, oh, it's because I accidentally misspelled print.

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My bad.

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Let's go ahead and try that again.

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We'll hit run.

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And there we go.

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It says.

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And Bob said, we get a new line created where this second part of the string is printed, and it says,

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today was a crazy day.

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And as you can see, it has included our quotation marks.

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So that was the role of that first escape character, the single backslash, and then that other escape

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character, the backslash n moved all of this other text in our string to a new line.

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Another escape character I like to demonstrate to you is backslash t.

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So what I'm going to do is I'm going to set escape characters equal to a new string.

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And I'm just going to say example of and we can do backslash t escape character.

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Now, if I would actually like to include backslash t inside of the text, what I'm going to have to

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do here is I'm going to have to create another backslash t, but instead I'm going to put another slash

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which is going to omit this original slash, which means these two characters right here are going to

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be included inside of my string.

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And then afterwards we have our escape character right here.

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And what this is going to do is it's going to insert a horizontal space within our string.

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So that means example of slash T and then escape character.

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There's going to be a big gap between these two.

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So let me print this out inside of the console and let me not misspell it again.

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And then we can hit run.

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And as you can see, we get an example of backslash t.

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We get our gap and then escape character.

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So as you can see it has inserted a horizontal spacing between these two strings.

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Now, these were just some of the main tools at your disposal to manipulate strings.

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You should now have a good understanding of the string library and text manipulation inside of your

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scripts.

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I will see you in the next lecture.