Easy Programing

ลำดับตอนที่ #9 : Go I - Conditionals & Booleans

Using if Statements

What is Control Flow?

For the rest of this lesson, we will learn about control flow. When programming, it is common to decide which part of the program to run based on certain conditions. For example, "Changing grades (command) is based on the test score (condition)" is an example of control flow.

if Statements

if statements allow you to create a control flow that means "if X, do Y". An example of how to write an if statement is shown below. Write the conditional statement after if, and run the code inside {} when the condition is true. Continue to the next slide for more!

if Statement Conditions

Symbols used to compare values are called comparison operators. Some, like < and >, are written the same way as in math. However, symbols like >= (greater than or equal to) and <= (less than or equal to) from math are written like >= and <= in Go. if statements in the form: if conditionalStatement { }.

Boolean Values

Let's look more at conditions used in if statements. When a conditional statement using a comparison operator in the if statement is printed, "true" is displayed in the console. What does this "true" mean? Look at the next slide to find out!

What are Boolean Values?

The "true" printed in the previous slide is something called a boolean value. The data type for boolean values is called "boolean type" and it has two possible values, true or false. Conditional statements with comparisons are true when the comparison is true and false when they are not.

if Statements and Booleans

Using what you learned about booleans into account, let's take another look at if statements. The code inside an if statement will run when its condition is true and are not called when it's false.

Comparison Operators

Comparison operators are not only symbols that compare the size of values, like > and >=. There are also symbols used to compare the equality of values. In mathematics, _"%=_%" is used when both sides are equal, but in Go, since = is for assignment, "equality" is shown using the == operator.

Recap of Booleans

The figure below recaps the most common comparison operators that you learned in this lesson. 

else

Handling False Conditions

With if statements, you have already learned how to run specific code when a condition is true. Next, let's learn how to write a different kind of control flow to deal with conditions that are false.

else

By using else with if statements, you can write a control flow meaning "if X, then Y, but if not then Z". Here, when the if statement condition is false, the code in the else statement will run.

else if

If you want to add a branch for when the condition of an if-statement is false, use else if. The control flow "if A then B, if X then Y, if neither then Z" can be created using else if!

else if statements can be used any number of times, but they will run in order from the top down. This means that only the code in the else-if with the condition that is true first will run.

Combining Conditional Statements

and (&&)

Let's learn how to combine multiple conditional statements. The conditional "if condition1 and condition2 are true" is written like condition1 && condition2, using &&. Here, && means "and". When combining multiple conditional statements with &&, the statement will only become true when every condition is true.

or (||)

The conditional statement "if condition1 or condition2 is true" can be written like condition1 || condition2 using the || operator. When multiple conditions are combined with ||, if any of them are true, the enitre statement will be true.

Negation (!)

The ! operator is used to negate a condition, giving the opposite result. Therefore, the code !(conditionalStatement) will become false if the conditional statement is true, and true when it is false. 

switch

The switch Statement

This is the last exercise! In control flow, switch statements can be used instead of if statements. switch statements can be written as shown below. When the conditional value matches the case value, the code for that case will run. The structure of switch statements is a bit complicated. (The "default" will be explained later on.)

if Statements and switch Statements

Let's compare examples of a switch statement and an if statement. On the right, the content will be called when the conditional value and case value are == (equal). When the control flow is based on "what the value is (x % 2)", switch statements can be written more easily.

Designating Multiple Values

Multiple values can be specified using commas ( , ) after the word case. When multiple values are used, the code for a case will run if the condition value of the switch matches either one of them. This is similar to using multiple conditions with the logical || (or) operator.

default

In switch statements, the content that will be run when none of the cases fit can be specified with the default case. This is similar to the way else is used in if statements.