How to Increment and Decrement Numbers in Solidity

Incrementing numbers in Solidity is straightforward:

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.17;

contract Counter {
    uint public count = 1;

    function incrementCount() public returns (uint) {
	    count++; // or count += 1
	    return count;
    }

    function decrementCount() public returns (uint) {
	    count--; // or count -= 1
	    return count;
    }

    function incrementCountByX(uint x) public returns (uint) {
	    return count += x;
    }

    function decrementCountByX(uint x) public returns (uint) {
	    return count -= x;
    }
}

However, developers should consider the effect prefix (++i/--i) and postfix (i++/i--) operators have on return values in advanced use cases. From the docs:

a += e is equivalent to a = a + e. a++ and a-- are equivalent to a += 1 / a -= 1 but the expression itself still has the previous value of a. In contrast, --a and ++a have the same effect on a but return the value after the change.

For example:

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.17;

contract Counter {
    uint public count = 1;

    function incrementCountPrefix() public returns (uint) {
		// the count variable is incremented and the function
		// will return 2 (or the value after the operation)
	    return (++count);
    }

    function incrementCountPostfix() public returns (uint) {
	    // the count variable is incremented but the function
		// will return 1 (or the value prior to the operation)
	    return (count++);
    }
}