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So so far, we've learned how to write a basic go program consisting of one file in a package, Maine,



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and we have that main function.



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So we've also learned how to to create basic functions that we can call from Maine, how to store variables



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and how to create our own types of variables with structures and types.



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And we've learned about maps and slices.



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One of the things that you need to know, and we're going to do it right now is how to make decisions



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in a program, Engo in particular.



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So the conventional method for making a decision is the IF statement, and it's really easy.



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If you've worked in any other programming languages, you'll have no problem with it whatsoever.



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And the syntax is simple.



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If some condition, then we're going to do something, otherwise do something else or don't do anything



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at all.



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So let's just give it a try.



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Well, first of all, create a variable and we're going to have a variable, which I'll call is true.



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And I'm going to give that a shorthand syntax and I'm going to say true.



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This is a type of bool which we haven't actually seen yet.



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So let's do the other way of looking at it.



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Just so you're familiar with the type var is true is a bool, which is a boolean, which means it can



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only hold two possible values, true or false, and will say is true, is equal to trip.



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And then we'll do a simple if statement.



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If is true then in print then we start our curly brackets log print line.



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True is true is followed by the value of is true.



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Is true.



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ELT's loved print line is true, is is true, same thing, and that's all we're going to do.



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So if you think about this, it's a very, very simple program.



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I've created a variable called Is True and I've assigned it the value of true.



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And then I use go to say to to test that value if is true, which is saying exactly the same thing as



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saying if is true is equal to true.



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And what I say is the double equals sign here because that's a comparison.



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It is true is equal to true print this otherwise print that lets run it.



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Go run maeng go.



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And what do you think is going to happen.



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Pretty simple is true.



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Is true.



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Which is a really weird sentence when you think about it.



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Let's try that again.



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The variable named is true has the value of true.



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Therefore what's here on line ten.



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We'll get executed and what's here on line twelve will not get executed.



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In other words, it should print out to the terminal.



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Is true.



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Is true.



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And it does and if we come up here and change is true to false, then it should print this letter instead.



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So let's clear the screen and run it.



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And it should print is true, is false, and it does.



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So that's a basic if statement, if statements can become more complex than that, but not difficult



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at all.



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So let's try something else.



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Let's create a new variable called cat is assign the value of cat and let's do it if statement if cat



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is equal to cat log dot.



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I've got to get inside the brackets there.



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Logged print line cat is is Cat Elz, and again, inside those curly brackets, log gridline cat is



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not cat again very simple will run it because Cat is assigned the value of cat.



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That first one should actually get printed.



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And it's given me a warning saying cat is always true.



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But I know that because I'm just trying to demonstrate something here it was a cat is a cat and if I



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say Cat two instead of cat it should put the second one.



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Cat is not cat.



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Cat is not cat.



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OK, let's try it with numbers.



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My name



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is equal to or is assigned the value of I'll use.



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The shorthand is assign the value of one hundred and this time I'll do a second variable as well.



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Is true is assigned the value of thoughts.



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What if I want to test two conditions which is what I'm trying to demonstrate here.



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If my name is Tomago greater than ninety nine and I'm going to use a double ampersand to say I want



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to have this condition and another condition is true.



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Then log, print line.



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My name is greater than 99 and is true, is set to true.



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Now what's going to happen if I run this program first?



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I've been passing in two conditions and both of these have to evaluate to true in order for this to



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take place.



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So the first condition is the number of the variable stored in myname has to be greater than 99.



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And the variable is true, has to be set to true.



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Is are both of those conditions true?



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Well, is 100 greater than 99.



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Yes.



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Is is true.



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True.



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No, it is set to false because one of these conditions is false.



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This will never execute.



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So if I ran this program, nothing should happen.



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Let's clear the screen, run the program and nothing happens.



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Exactly.



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Now, if I change this, if I say and is true, is equal to false, I could do it like this is true



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is equal to false.



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And this time of year in the program, it will run and it will print it out, which is exactly what



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I wanted.



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But there's a shorthand.



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So instead of saying is true, is equal to true, I can put an exclamation mark in front of it which



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says not so if my name is greater than 99 and is true, is not true or not, is true, in other words,



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is to is false.



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This should run and it does.



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And it prints out the line exactly as I expected.



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And if I wanted to, I could put at else condition here, just as I did before.



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And in fact I can go else ELT's ELT's, I put something in here.



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So else if my number is less than one hundred and not and is true, which is the same thing as saying



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and is true is true.



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OK, and here I could have a third condition if myname



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is exactly equal to 101 or is true.



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Elusive, my name is greater than 1000 and is true, is equal to faults or not is true.



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I can have all of those and I have an area.



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One is this is truly mine, a much greater thousand and is true equal to faults, evaluative, but not



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used.



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Right.



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I got to put something in there so I could just put log print lines and I'll just put really simple



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things in there.



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One



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to three.



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OK else if they're so now I can change these values and depending on what I change them to, one of



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these conditions might execute.



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So you can have as many Elsas as you want and in a statement, but honestly, you probably never want



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to have more than one or two eltis.



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I only ever go with one in the vast majority of cases.



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Usually I test a condition and if it evaluates to true, I want to do something.



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Otherwise I want to do something else.



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If I have something that's more complex than that, then than that.



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And I have more than two things, have two situations or two cases I ever want to handle, I chances



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are I'm not going to use an if statement.



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I'm going to use another decision structure which is which exists specifically for this kind of situation.



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So I'm going to delete everything out of this.



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And I clear the screen down here and we'll go to another decision structure called the switch statement.



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And the switch statement is really easy.



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So you simply say switch it on some value, which I'll call my var, which I haven't created yet, but



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I will in a minute switch on my var and then you have cases and you have a case and some value.



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So let's create my var.



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So this makes sense.



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My bar is assigned the value of cat and I'm going to switch on my var inside of those, these brackets



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I'm going to have key statements.



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So the first one is to say if the if my var has the value of cat do something.



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So I put case followed by the value I'm looking for or the condition I'm testing for, followed by a



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corn and then do something like the print line cat is set to cat and I better use lower case here.



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Not confused myself then I can have another case.



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Which has to come here, of course, another case, case dog and then do something, so I'll copy this



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and paste this in here.



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Cat is such a dog that I might have a third one, which I copy the whole thing and pass it down and



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put it in the right spot again.



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And fish cat is set to fish.



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Now, I have an error somewhere.



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What is it?



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The error is I get an extra quote hidden down below the scroll here, extra closing bracket.



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All right, so now I have a switch statement.



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So I have a variable called cat called my Vah, which is set to cat.



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And then I switch on it and I switch on the variable, my version.



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And I simply say, if that variable happens to equal cat do this, if it happens to equal dog, do this,



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if it happens to equal fish, do this and then I can have a special case default, which is to say,



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if none of the above conditions are true, do this log print line and keep putting these in the wrong



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spot for some reason.



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Default.



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Logged print online cat is something else, and I saw what I have to do.



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So let's think about what's going to happen here.



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I've established this variable.



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I created this variable called my version of assign the value of Cat to it.



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Then I switch and I handle a bunch of cases and I can have as many cases as I want.



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Check this valuable mirror and compare it against all of these cases.



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So one is cat is cat equal to cat?



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Yes, it is.



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Therefore, this will happen.



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Now, in other programming languages that implement the switch statement, you actually will keep going.



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You keep testing to see do you meet any of these other conditions.



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So if the condition was case cat or and then case some other condition that matches it, it would keep



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going.



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And if it matched three of the cases, it would do all three of those actions.



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Go does not do that go breaks out as soon as it matches one case.



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And that's something you have to remember.



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So if I run this program, it should print out cat is set to cat.



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Let's try it.



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Go run Mingo Cat said the cat.



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If I said Cat two dog and run the program, it should print out the case that matches dog and cat,



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said the dog.



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If I said it to horse, it doesn't match any of these three cases.



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What's going to happen?



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Well, it's going to execute this default case.



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So let's run that program and see what happens.



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Cat is set to something else.



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So those are your two basic decision structures.



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The IF statement, which you use a great deal of the time, and the switch statement which you use periodically,



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particularly when you have to make a decision based upon a lot of different cases.



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There is a third one, but we're not going to get to that for a little while.



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So bear in mind that the two main ones we've covered right now, the if statement and the switch statement



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and the third one will get to a little bit later on.



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That's enough for this time around.