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[No Audio]

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Hello and a warm welcome again

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in the new section of the course.

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This section intends to cover the

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basic programming constructs called the

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control structures, that are part of almost

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all programming languages. control structures

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are the constructs, that analyze variables and

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choose directions in which to execute the

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code, based on some parameters. The basic

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control structures in programming languages

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are conditionals. Conditional statements or

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conditional expressions are also sometimes

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referred to as conditional constructs or

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programming language commands for handling

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decisions inside the program.

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The first, and very basic type of conditional construct,

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which is used in almost all the programming

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languages, is the If conditional statement.

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This tutorial will discuss this in detail, so

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let's start with today's learning agenda.

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The first question is, when the if statement is

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being used? We use it when we need to execute

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a block of statements or code segment, when a

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certain condition is being true. Let us look

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at the general syntax for the if statement,

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which will make things more easy to

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understand and comprehend.

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[No Audio]

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The statements inside the curly brackets, are

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referred to as the body of the if statement,

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and they will only execute if the given

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condition in front of the if statement

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evaluates to a value of true. In case the

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condition is false, then the statement inside

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the if are skipped, and the remaining code

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after the ending curly brackets, are executed

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as normal. Let us have some examples. I will

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declare a variable some_number and

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will assign to it a value of 40.

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[No Audio]

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Next I will check, if the value of some_number

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is less than 50.

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[No Audio]

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If it is true, then I will display the

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message, the number is less than 50.

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[No Audio]

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Outside the body of the if statement, I will

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add another print statement which will

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execute, irrespective of the condition

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in the if statement.

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[No Audio]

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In this case, now since the condition in the

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if statement will be true, as the value of the

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variable is less than 50. Therefore, the

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print statement inside the if statement, will

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be executed. The statement outside the if

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statement, since it is not associated with any

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condition, so this statement will also execute.

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Let us Cargo run to confirm.

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[No Audio]

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if I change the value of the variable, to that

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of, let's say 55 and execute again.

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You may note that, the statement inside the if

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statement is not executed, but the statement

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outside the if statement has executed.

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[No Audio]

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This is because, there is no condition associated with it.

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Okay now, let us move ahead. The

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condition in the if statement, can be composed

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of multiple conditions that are joined

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together using the logic operators, such as

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the AND and OR operations. Let us see an

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example on this. Let me first declare a

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variable of marks, and assign it a value of 65.

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[No Audio]

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Let us now check, if the student marks are

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in a certain range, let's say in the range of 60 to 70.

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[No Audio]

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For the marks to be in this range,

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we will have conditions to check that they

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are greater than or equal to 60, and less than

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or equal to 70. The two conditions can be

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combined, with the help of logical AND

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operation. The logical AND operation will

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return a true, when both the conditions to the

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left of it, and to the right of it, are both

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true at the same time. The logical AND

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operation is indicated by the two && signs.

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[No Audio]

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If the marks are in the range, then we will

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display a suitable message.

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[No Audio]

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Let us execute this.

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[No Audio]

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This statement has been

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printed which indicates to us that the

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condition was overall true. Please note that,

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one & sign is used for a reference in Rust.

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And two & signs are used, for a logical AND

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operation. Similar to the logical AND

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operation, we can use the logical OR operation

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to construct the conditions for the if statement.

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Let us do an example on this.

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I will declare a couple of Boolean variable,

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called flag_1 and flag_2.

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[No Audio]

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Next I will set condition, if flag_1 == true

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or flag_2 == true, then the body of

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the if statement should be executed.

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The logical OR is mentioned using two vertical

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pipes, let me add a suitable display message

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inside the if statement and execute.

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[No Audio]

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The message is displayed,

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which means that the conditions it will await

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it to true. If we want to construct a

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condition by checking if two things are

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equal, then we will use two equal signs

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instead of one equal sign, between the value

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of the two items. Negation operation can also

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be used to construct the conditions, let us

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also learn this.

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I will create a boolean variable,

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and we'll assign to it a value of true.

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Next, I will check if the value of the

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flag is not equal to false, is true or not.

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If flag is not false, then this condition will be true.

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Since flag is not false, therefore,

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this condition will evaluate to a value of true.

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Let us confirm this by adding suitable

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print statement, and then execute.

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[No Audio]

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We can always combine the simpler expressions

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involving AND or OR operation to make more

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complex conditions. Let us see detailed

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examples on this.

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I will define two boolean

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variables, and one integer variable with a value of 60.

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[No Audio]

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I will now construct a complex condition, by

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setting flag_1 == true,

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and a flag_2 == false,

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or number < 50

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[No Audio]

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This condition has two parts, the first

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part will be only true, when both the

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conditions are true. That is flag_1

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has a value of true, and flag_2

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has a value of false. The OR outside the

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brackets means that, either the condition to

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the right, or to the left is being true.

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That is for the overall condition to be true,

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either the value should be lesser than 50, or

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the value inside the bracket should be true.

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Since the value is not lesser than 50, so we

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will consider the first part, where both the

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conditions are true. So therefore, the entire

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condition is true. Let us add a suitable

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print statement to the body of the if

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statement and execute.

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[No Audio]

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The complex condition has evaluated to true.

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Please note that, if I change the brackets and

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enclose the second and third conditions

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together inside the small brackets, then this

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expression will have a different meaning.

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This means that you have to pay special

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attention when aiding smooth brackets for

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constructing complex expressions. Okay, now

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we will learn some variants of the basic if

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statement. The first variant is called if else

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conditional statement. Let us start from

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the general syntax first.

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[No Audio]

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If the condition associated with the if

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statement is true, then the statements inside

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the body of if are executed, and the statement

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inside the body of else are skipped and not

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executed. On the other hand, if the statement

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associated with the if statement is false,

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then the statement inside the body of the

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else are executed, and the statement inside,

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the body of the if are skipped from execution.

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Let us understand this with the help of an example.

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We will declare a variable of marks,

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from a value of 80.

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[No Audio]

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Then we will check if marks > 50,

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then I will print the statement

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that you have passed, and if it

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is not true, then in the else part,

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I will print the message that you have failed.

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[No Audio]

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Let us execute to see the result.

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[No Audio]

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The candidate has passed. Another frequently used

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variant of the if statement, is the if else, if ladder.

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We will start with the general syntax.

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[No Audio]

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The conditional expression in this case are

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evaluated from top to bottom. As soon as a

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true condition is found, the statement

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associated with that if statements are

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executed and the rest of the ladder is

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skipped. In other words, the conditions are

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checked in sequential order and the body of

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the first condition happening to be true is

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only executed. If none of the conditions

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are true, then the else part will be executed.

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Also note that the else included at

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the end is optional. Let us understand this

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further, with the help of an example. I will

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write a simple program, which based on the

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marks of the student, will assign a suitable

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grade to the student. I will create a

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variable which will contain the marks of the

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student, and initialize it from a value of 95.

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Now based on the marks, I will assign a

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letter grade to the student. To store the

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grade, I will declare a grade variable and

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will initialize it from a value.

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And is a sort of default value, having a meaning of no break.

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[No Audio]

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Now, I will first aid conditions

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for the maximum grade, which is A, and it is

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given to a student securing greater than or

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equal to 90 marks, so let me code it.

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[No Audio]

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The next grade is B, which corresponds to

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marks greater than or equal to 80.

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[No Audio]

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Next comes the grade of C, which corresponds

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to marks greater than or equal to 70.

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[No Audio]

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The next grade given on marks, greater than or

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equal to 60.

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[No Audio]

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In the optional else part, I will assign a grade of F.

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Let us also add a suitable display

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message for printing the student grade.

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[No Audio]

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Let us execute to examine the grade.

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[No Audio]

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The grade is A in this case, the first if statement

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happens to be true in this case, and

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therefore, the grade was being set to that of A.

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Although the remaining conditions are also

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true in this case, that is the marks are also

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greater than or equal to 80, and 70, and 60. But

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only the body of the first if statement is

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being executed. This is because as pointed

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out earlier also, in the if-else ladder, the

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conditions are checked in sequential order,

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and the body of the first condition happening

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to be true is always executed. That brings us

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to the end of this tutorial. Our discussion

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on the if statement is still not complete and

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we will discuss some of its variants in the

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next tutorial also. Along with another

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relevant statement, which is very frequently

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used in Rust, called the Match statement.

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That will be fun and exciting, so do come back for

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learning that. And until next tutorial,

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happy Rust Programming.

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[No Audio]