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Vectors are a resizable array of elements allocated on the heap.

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Vectors are an essential type and rust because they are used almost anywhere.

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One needs a list of dynamic size.

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The easiest way is to use the VEC macro and as a reminder, we will talk more about macros later on

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in this course.

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But for now let's just look at how to create a vector using the VEC macro.

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So I went ahead and created a new variable called nums and we are going to use the VEC macro to create

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a vector.

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So I'm going to put in the values one, two and three.

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And now remember I said that vectors are resizable, so let's add a value into this vector already and

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call it and give it the value four.

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So now let's print this out and see how it works.

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Now this is going to produce an error, but I want you to see the error so that we can understand why

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it's an error.

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So it says vec of type integer cannot be formatted with the default formatter.

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So if we continue reading down and this is just showing you how helpful the rust compiler is, it will

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say you may be able to use a colon and a question mark.

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Instead.

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So basically what that is, is that's going to allow us to put it into debug mode.

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That's what the question mark is.

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And the the colon basically says, take the next thing and then push it into the formatter and output

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it into debug mode.

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So now that we have that in there and we cargo build, don't forget to make your variable mutable since

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we are changing it by adding it another number.

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And now we can see we have the values one, two, three and four printed out.

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But we can also remove values, so we can use the pop method that a vector provides us.

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And what pop is going to do is it's going to take the last value that we pushed into the vector and

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remove it.

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So let's pop one and then let's print it out.

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And it should remove the four from the vector, which is exactly what it did, which is awesome.

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So there is another way that we can create vectors.

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So let's go ahead and do that.

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And it's called Vec Nu.

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So when we use the macro, this is essentially.

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What it's calling is the new constructor.

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So now that we created a new empty vector, again, we can push values onto here.

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So let's call it test and then let's push on.

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String.

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Let's print it out.

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Just to make sure that we are working correctly.

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Clear it.

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Build it.

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Run it.

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And we have test string.

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So now what's really cool about vectors, they come with a ton of methods that we can already use.

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So I highly encourage you to explore all these methods after this lecture, just to really familiarize

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yourself with everything available in the vector class.

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So what we're going to do, just for an example, is reverse.

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Vector that we created.

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So by doing this, we should see when we print it out.

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String test.

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Which is exactly what we got.

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We have string test.

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So again, I highly encourage you that after this lecture just play around with all the different methods

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that a vector provides and just really get familiar with them as they will help you in your rest career.

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So another really cool thing that we can do is if you know the size that your vector is going to be,

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we can actually specify that.

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So let's start off with a new vector and we'll call this one vector and we're going to say Vec.

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Now we have to give it a type since we are creating it empty in this case.

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So I'm going to give it integer 32 with capacity two and then I would just want to print out just to

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make sure that it created.

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That capacity effect dot.

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Book passage.

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Here we go.

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So let's build it.

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We have an issue here.

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It says, use fully qualified syntax.

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So we said, let me vet.

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Vet of type I.

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32.

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With capacity to.

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Let's see if we can use the compiler to figure this issue out.

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So I know that this one's not going to work.

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And it's because we needed.

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Greater than and less than around it.

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So now that we use the compiler to figure it out, let's go ahead and run it.

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So down here it says to which is what we set our capacity to be at.

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So you might be wondering, well, if I create a vector with capacity to what happens if I end up needing

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extra capacity?

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Luckily the vector can grow if it needs to, and the way it works is it's going to allocate a larger

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buffer, copy the present contents into the new buffer, and then it's going to update our vector variable

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to point to the new buffer, and then it's going to free the old vector from memory.

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So basically it's just going to get a new region of memory, push everything into it, and then delete

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the old.

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So that way it's very seamless for us to be able to expand it as we need to.

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And then one other trick I want to show you is you can actually create a vector.

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Using an iterator and we will talk about iterations later on in this course.

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So we'll say we want to create a vector from value 0 to 5, not including five.

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And let's go ahead and print it out.

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And it should give us values zero, one, two, three and four, which is exactly what we got down here.

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We have values zero, one, two, three and four.

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So again, I highly encourage you to play around with all the methods available to vectors to really

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familiarize yourself with them.

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It is a very essential type in rust and it will immensely help you as you continue to learn rust.

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And the next lecture, we will talk about what slices are.