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In this lecture, we are going to start our journey by learning about variables.

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This course assumes you have some experience with programming.

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Learning a new language is much easier the second time around, while the syntax may be different.

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The concepts are very similar from language to language.

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Variables are still variables.

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Functions are still functions.

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Conditional statements are still conditional statements, so on and so forth.

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You get the picture variables in rust serve the same purpose as variables in other languages.

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Their containers for data throughout this course, we will be working inside these source slash main

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RC file.

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I recommend opening this file before starting a lecture.

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Inside this file cargo has defined a function called Main.

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I know we said we would start with variables, but let me quickly introduce functions.

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Functions are blocks of code for performing a particular task.

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If you have a background in JavaScript, you would use the function key word to define a function for

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Python developers.

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You would use the defined keyword for US developers.

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Function definitions start with the FN keyword.

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It's all the same.

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The FN keyword is followed by the name of the function.

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A list of arguments and then the lock of code.

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Our apps must define a function called mean.

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By default, Cargoe will search for a function called mean during compilation.

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If we were to rename this function, the compiler would complain.

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It's always guaranteed this function will run.

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Once we're going to empty, the contents of the function will be starting fresh.

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The main focus of this lecture is variables.

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We can declare a variable by typing the let keyword.

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Next, we can give our variable a name for this example.

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Let's set the name to my name for the value.

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We're going to store our real name or whatever name you prefer.

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After declaring this variable rust is going to throw a warning.

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Assuming you have the rust extension enabled, there should be a yellow squiggly line below the variable

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name.

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We can hover our mouse over the variable to learn about the error just in case.

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If you don't see an error, you can produce the error by running the cargo run command in the terminal.

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The compiler won't hesitate to output the same error regardless.

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The error message should be the name, according to the compiler.

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There's a problem with the variable name.

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At times, rust can be an opinionated language.

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Variables must be snake case.

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They can't be camel cased.

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It's a standard practice in rust projects.

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Let's convert the variable name to snake casing.

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Learning to adopt a specific formatting practice can be tedious, especially if you're used to writing

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code differently.

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However, it's worth it to be consistent with the community.

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There are a couple more features I want to point out.

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Firstly, statements must end with a semicolon.

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If you have a background in JavaScript or Python, semicolons are optional.

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Statements in rust must end with a semicolon to indicate the end of the line.

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If we were to remove this character, the compiler would throw an error.

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Errors are indicated in the editor with a red squiggly line, according to the compiler.

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It expected a semicolon.

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Let's add it back in.

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Moving along, another warning gets thrown by the compiler surrounding the variable.

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The error will tell us the variable is unused.

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For this example, we are going to ignore this warning.

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It's not the end of the world.

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All right.

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One more thing before we move on to the next topic variables are immutable.

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Mutability is another way of saying a variable can't be changed once a variable is initialized.

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We can't change it to another value, therefore they're immutable.

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This design forces developers to be aware of how their variables will be used.

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That doesn't mean mutability is bad.

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It is possible to make a variable mutable.

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Let's try mutating the my name variable to a different value.

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An error gets thrown by the compiler.

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It's telling us we can't modify an immutable variable.

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Variables can become mutable by adding the multi keyword before the variable name.

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Let's add this keyword to the my name variable.

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With a single keyword, the air has gone away.

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Mutable variables must be explicitly declared with the mute keyword.

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You should keep this in mind when working with variables.

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Let's continue talking about rust in the next lecture.