Library contracts in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a library named MathLib.

Blockchain / Solidity

library [1] {
    function add(uint a, uint b) internal pure returns (uint) {
        return a + b;
    }
}

Drag options to blanks, or click blank then click option'

AMaths

BMathLibrary

CMathLib

DLibMath

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different library name than MathLib.

Forgetting the library keyword.

The library name must be MathLib as declared in the code.

2fill in blank

medium

Complete the code to use the library function add for uint variables.

Blockchain / Solidity

using [1] for uint;

contract Calculator {
    function sum(uint a, uint b) public pure returns (uint) {
        return a.add(b);
    }
}

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ASafeMath

BUtils

CCalcLib

DMathLib

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong library name like SafeMath or Utils.

Forgetting to use the using keyword.

The using directive must refer to the library MathLib to use its add function.

3fill in blank

hard

Fix the error in the library function declaration to make it a pure function.

Blockchain / Solidity

library MathLib {
    function multiply(uint a, uint b) internal [1] returns (uint) {
        return a * b;
    }
}

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Apure

Bview

Cpayable

Dexternal

Attempts:

3 left

💡 Hint

Common Mistakes

Using view instead of pure.

Marking the function payable or external incorrectly.

The function should be marked pure because it does not read or modify state.

4fill in blank

hard

Fill both blanks to declare a library function that returns the minimum of two uints.

Blockchain / Solidity

library MathLib {
    function min(uint a, uint b) internal [1] returns (uint) {
        return a [2] b ? a : b;
    }
}

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Apure

Bview

C<

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using view instead of pure.

Using the wrong comparison operator >.

The function is pure and uses the less than operator < to find the minimum.

5fill in blank

hard

Fill all three blanks to create a library function that checks if a number is even.

Blockchain / Solidity

library MathLib {
    function isEven(uint num) internal [1] returns (bool) {
        return num [2] 2 [3] 0;
    }
}

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Apure

B%

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using view instead of pure.

Using != instead of ==.

Using wrong operators for modulo.

The function is pure. It uses the modulo operator % to check if the remainder is equal to zero.