Lesson 6 of 34
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# Functions

##### Yasin Cakal

In Solidity, functions are blocks of code that can be called and executed at any time. Functions are a key concept in programming and are used to organize and reuse code, making it easier to develop and maintain complex programs. In this article, we’ll take a closer look at functions in Solidity, including how to define and call functions, and how to use function parameters and return values.

## Defining Functions

In Solidity, functions are defined using the “function” keyword followed by the function name and a set of parentheses. The function name should be a descriptive name that reflects the purpose of the function.

For example, the following code defines a function called “incrementCounter” that increments a counter by one:

function incrementCounter() public {
counter++;
}


## Function Parameters

Functions can accept input in the form of function parameters. Function parameters are specified in the parentheses after the function name, and they allow the function to accept and process different values each time it is called.

For example, the following code defines a function called “addNumbers” that takes two integers as parameters and returns their sum:

function addNumbers(int a, int b) public returns (int) {
return a + b;
}


## Function Return Values

In Solidity, functions can return a value using the “return” keyword. Return values allow a function to pass data back to the calling code, allowing it to be used or processed further.

To specify the data type of the return value, use the “returns” keyword followed by the data type in parentheses after the function definition. For example:

function getAge() public returns (uint) {
return age;
}


This code defines a function called “getAge” that returns an unsigned integer (uint).

## Calling Functions

To call a function in Solidity, use the function name followed by a set of parentheses and any necessary arguments. For example:

incrementCounter();

This code calls the “incrementCounter” function.

If the function takes parameters, you can pass them in the parentheses. For example:

int result = addNumbers(3, 4);

This code calls the “addNumbers” function with the arguments 3 and 4, and assigns the returned value to the “result” variable.

## Conclusion

In conclusion, functions are a key concept in programming that are used to organize and reuse code. In Solidity, functions are defined using the “function” keyword, and they can accept parameters and return values. Functions can be called and executed at any time, allowing you to reuse code and make your contracts and decentralized applications more efficient and maintainable.

## Exercises

To review these concepts, we will go through a series of exercises designed to test your understanding and apply what you have learned.

#### What is a function in programming?

In programming, a function is a block of code that can be called and executed at any time. Functions are used to organize and reuse code, making it easier to develop and maintain complex programs.

#### How are functions defined in Solidity?

In Solidity, functions are defined using the “function” keyword followed by the function name and a set of parentheses. For example: “function incrementCounter() public { counter++; }”.

#### What are function parameters?

Function parameters are specified in the parentheses after the function name and allow the function to accept and process different values each time it is called.

#### How do you specify the data type of a function’s return value in Solidity?

To specify the data type of a function’s return value in Solidity, use the “returns” keyword followed by the data type in parentheses after the function definition. For example: “function getAge() public returns (uint) { return age; }”.

#### How do you call a function in Solidity?

To call a function in Solidity, use the function name followed by a set of parentheses and any necessary arguments. For example: “incrementCounter();”. If the function takes parameters, you can pass them in the parentheses. For example: “int result = addNumbers(3, 4);”.