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In this lesson you're going to talk about one of the most fundamental aspects of any programming language

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or an algorithm and that is a conditional statement or what you call it if else statement which is some

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sort of a control flow.

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What it does for us is it helps us compare two or more objects of values or variables against each other

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and depending on the result of the comparison we could do different things.

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So let's go ahead and see this in practice so we get a better understanding of what it means as a concept

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and then jump back into X code.

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I'm going to close this project Stop this time and I say give me your command line tool.

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And this one is called if else project.

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So I might if else project I'm going to go into my main as usual when I get rid of all the comments

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and then reformat everything nice and tidy.

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And here is how I'm going to write my first if else statement.

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Imagine a situation like this.

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Imagine I have an integer called A which is 5 and I have another integer called B which is 6.

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Now what they could do is I would say if A is larger than B then do this and this large say A is large

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as simple as that.

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Now we all know if I run this application now it's obviously nothing is going to happen simply because

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in this case 5 is not bigger than 6 5 is actually smaller than 6.

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So what if I wanted to have the are there a statement.

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What if this wasn't true.

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So I'm going to go ahead and say let's do this and this long b is larger and then rerun this code and

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now it says B is larger B is bigger.

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Now that we saw it once in practice let's better understand what it does essentially.

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And if the situation depends on a condition which is here within this is that is either true or false.

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So the condition that we feed into that if a statement is either true in which case the if part will

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happen or it is false that the else or the L says will happen.

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Talk about the Elsa's soon how we could have more than one else but let's see a different kind of practice.

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Let's say I had to remove all of these.

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So I had Boullion my Boullion was meant to walk are nuts for that or is fetched.

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So that is true.

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Obviously this is not something that I would make a static kill like this we would make this depend

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on some other arised you.

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And then based on that they would decide whether or network data is fetched or it is still we're still

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fixing their ideas.

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But based on that they could say if that is a fetch.

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So their value is true or false if that's the case say and Aslaug we got the data and then if it is

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else in the house you could for instance say and it's like still reading for instance or something to

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that effect.

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So again we have an if else a statement that works based on a boolean result of a conditional.

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So the format of any false statement is essentially like this.

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I have that.

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So I have if condition and then if in case of true and then else in chase all from Faux now a little

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bit earlier I said about the fact that there might be more than one else there might be Ellis says happening.

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Let's see that once again and let's see how that could be the case.

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And will writes My original quote in a five city is six and I'm going to say if a is larger than B then

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obviously you say and this long a is bigger and this is what happens in the else in the else a is either

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a smaller than B because that's not true or 8 is actually equal to be.

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So let's see both of those in the else I'm going to say then if a is smaller than B then say and Aslaug

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and this time say a is a smaller.

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Simple as that.

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And there isn't else.

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If not neither of these two situations are correct.

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A is not larger than.

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So we ended up in the US in the ass 8 is another smaller than B then it means and it's like a is equal

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to B and we can actually test.

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Let me just get myself a little better for my thing so I can show everything that's wrong this could

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of course right now that you say is a smaller but if they were both six for instance I read around this

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chord is going to say a is equal to a B because it is flawed.

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It didn't work.

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It went to the else within the else.

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It says Well is it a smaller.

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That wasn't the case so it ended up in this one.

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Let's rewrite this a little bit differently.

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So I'm going to say if a is larger than B do that else if a is a smaller than B then I don't need to

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have this mess.

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That difference is statesman's.

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I'm going to remove that get through the fall of it kind of makes sense now.

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So I'm going to say if a is larger than B say is bigger.

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That makes sense.

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Else if a is a smaller than B say a is a smaller.

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What is the tared situation is neither larger nor a smaller.

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So else if neither of the two were correct say they are equal.

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That's about down.

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So you could either nest your false statements or you could use them in an else if situation.

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Keep in mind that the else if situation is best used when your partners are the same like when you're

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comparing a against B but you're not comparing a against B and C in that situation is much much better

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if you actually miss your if statements just like what we did a few minutes ago.

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Now in saying that let's say Now you want to expand your if statement into covering more than just the

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sign of being larger or smaller.

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What if you want to know if it is larger or equal.

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So I'm going to rewrite this.

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Say if a is larger or equal to B say and Aslaug larger or equal and obviously there is no to else there's

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only one else in here and that is.

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And this law is smaller so because it is neither larger nor equal it will be a smaller and larger or

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each one.

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What if I wanted to test if they're exactly equal.

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And this is an important one.

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So I'm going to say two equal signs and that is the sign of equality.

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If you remember earlier on we talked about how a single equal sign is a sign of assigning values assign

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values and two equal signs is a sign of comparing equality.

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So if I say if a is equal to be two equal sides it means I'm asking are they equal against each other.

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If that's true is going to print equal and then indeed as I could again write the same thing say well

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if a is larger than B do something and say Steve and Alice the last one do something else.

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So so far because these guys one larger is smaller than larger or smaller or larger or equal smaller

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or equal.

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There is another sign which is the not equal and that is how we use it.

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Are you going to say going to get rid of all of these.

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I'm going to say if a is not equal to be so if this is not happening.

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So that sign you could use either alone which I would show you or I could use it with an equal sign.

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So we could either say if a is not equal to B or we could say if this condition which is being true

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is incorrect.

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So you could use either of the two ways.

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But for now we're going to use the easier one which is like this.

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So I'm going to say if a is not equal to B then say not equal to B.

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And that's another one.

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Finally we should see how we can compare multiple different conditions against each other.

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So I have another one and see and that is seven and I want to perceive a and b are equal but if B is

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larger than c.

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So what you're looking for A and B called for it to be larger than c.

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So let's see how we could do that.

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I could go ahead and say just like what we have done before if a is equal to B.

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That's the condition I'm looking for in here B is larger than c then say and Aslaug.

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Yea this is the one that we were looking for.

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So that obviously works.

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But again we are nesting if statements.

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Maybe there is an easier way for it.

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And it absolutely is.

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And that is called.

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And so I'm going to say if a is equal to B and to signs B is larger than c it means if both of these

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conditions are true.

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So I'm gonna copy that and I'm going to put it there.

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So it's these two pieces of course they're exactly identical.

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This one means if a is equal to B and also B is larger than c.

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Now another thing that from time to time comes up is two conditions that we want.

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One of them to be true and then I had this seen here so far we saw and as are now in this next example

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I want to see this thing happen.

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A and B are equal or B larger than c.

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So I'm going to say if a equals B.

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If this is the right thing or is B is larger than c so this is the sign of.

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Or it means if this is true or this is true I'm going to be OK.

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Either of these three if it is correct then this part is going to happen.

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If none of them is correct then obviously the else part is going to happen.

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Sometimes you care about the spot sometimes you don't care about the else you just want the if part

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of your heart condition to be to happen.

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So I'm going to add this one in here as well.

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So that's a sign of or.

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And one last thing before I close this lesson and that is some values they can be compared against each

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other such as six again sevens against seven their boss or numeric models they are both integer values.

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If too hot to floats if you hada the two billion nonuse you could compare them.

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But for instance if you have two strings you can't just compare them against each other.

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Let's see that in practice.

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So if I have one and there's this thing called a string of one which says hello and then I had another

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string that is called the string.

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And this one is a random set of characters.

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Let's say it's a or b or a unique ID for something.

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Now I couldn't just going here and say You first two and one is equal to a string two simply because

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there is no such operator between the strings.

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The strings cannot be compared against each other like this.

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There result of this will always fail.

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So for situations like that there is a string or an array or a dictionary or things that you will see

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down.

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That's right.

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You actually have to use the builtin equality features of these de-friend you know rivals for instance

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in year I would say if a string of it doesn't matter which one comes first.

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But if casting one is equal to a string string two.

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So it's saying if this thing is equal to that the string and then obviously if it was true this part

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will happen in the else.

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The other part of it will happen obviously in this case.

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The other part is happening now that we are here I should quickly mention something else as well.

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Let me rewrite this.

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That's not the.

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The false statements or conditionals it's about the use of methods things such as this one.

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We have a lesson about this coming up in this very section.

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But I thought quickly you know I'll tell you about that.

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So what's going on here say is string to 1 and you see what I'm typing and this menu pops which is the

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auto completion menu.

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It tells me if it is of the type and it's a string so string one is equal to a string and you see again

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when the auto completion shows up and I'm typing that is equal to a string.

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It tells me you have to give me another string.

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So Carl I'm not on the string.

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So you have two feet and not interesting to me that is not all.

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It does have a certain value inside it.

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And on the left side of it it says I will give you back a Boolean I will give you a blank either true

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or false.

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So is equal to a string.

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Obviously here we have to feed the string get to the reason I brought this up is because whenever you're

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using any of these methods you have to keep an eye on what you have to feed into them.

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And also what you get back from them for instance if I had this mutable string this card it's my mute

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that is just nothing for an hour.

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And then I had a minute.

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It says it is and not over the string.

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Append the string.

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It says Well if you want to use the append the string please feed me with this string and I will not

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give you back anything because it doesn't return anything.

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It just does something on my mutable thing.

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I didn't see this much further in the future and that of text for instance we'll talk further about

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formatting different methods and using methods.

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But for now just so that you get some sort of familiarity whenever you're using any of these methods.

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Make sure that you read these values lot when you're using this tell yourself oh I have to feed it it's

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a string and tell yourself oh it's going to return a boolean.

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It says returns a boolean value that indicates whether this thing is equal to the receiver using a literal

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Unicode based comparison.

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And I'm going to say what if this one is equal to a string to.

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Obviously if you said and if statement is always based on a true or false and then based on that you

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can decide what's going to happen.

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So that's about that about using IF statements.

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Once again really quick to reach out and if statements are conditionals based on true or false.

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And they always are a part of the control flow and we will see more of the contraflow such as loops

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on a solve in the future lessons.

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So let's keep it up to here and we'll move on to our next.