Swap elseif code for switch case

Question

I’m having trouble modifying a code I made in else if for switch case. I’m not getting the code to work, he gets values and operation by $_GET and does the selected operation:

I leave the code here:

if((!is_numeric($num1) || $num1 == '' || $num1 == '0') && $operator == '/') 
    echo "ERRO: Numero 1 inserido e' zero";
else if((!is_numeric($num2) || $num2 == '' || $num2 == '0') && $operator == '/') 
    echo "ERRO: Numero 2 inserido e' zero";
else {
   //se a divisao for feita por zero, da mensagem de erro informando que o valor inserido foi zero
    if( !empty($operator) ) {
        if($operator == '+')
            $result = $num1 + $num2;
        else if($operator == '-')
            $result = $num1 - $num2;
        else if($operator == '*')
            $result = $num1*$num2;
        else
            $result = $num1/$num2;
        echo "O resultado é: ".$result;
   }
}

Answer 1

It would need to improve a lot, but basically it would be this:

if (!is_numeric($num1) || !is_numeric($num2) {
    echo "ERRO: as entradas precisam ser numéricas";
    //encerra de alguma forma, dpende do código.
}
$num1 = intval($num1); //pode  ser um floatval
$num2 = intval($num2);
switch ($operator) {
    case '+':
        $result = $num1 + $num2;
        break;
    case '-':
        $result = $num1 - $num2;
        break;
    case '*':
        $result = $num1 * $num2;
        break;
    case '/':
        if ($num2 == 0) {
            echo "ERRO: Não pode fazer divisão por zero";
            break;
        }
        $result = $num1 / $num2;
        break;
    default:
        //talvez mereça alguma mensagem de erro se não for nenhum operador válido
}
echo "O resultado é: " . $result;

I put in the Github for future reference.

Don’t convert to the switch what the if works best, do this only with the choice of operators.

Don’t forget to convert the values that are as text to numeric to do the account properly.

The test if it’s numerical is a little naive.

The test if the divisor value is 0 only needs to be done if the operator is split, then put it there. And the dividend can be 0.

There are several other things that could be done better.

Maybe the difficulty is because I wasn’t separating every responsibility. It is one thing to check whether the data is within the minimum standards to do something useful, another thing and select what to do. I don’t think it’s worth checking the conditional value separately (case of division by 0).

You need to see if you want only integers or decimal values as well. There are a number of other decisions to make good code for use. If it was a basic exercise then it would have been better to at least try to do what you wish.

Answer 2

You can try it like this:

    $num1 = $_GET['num1']; 
    $operator = $_GET['operator']; 
    $num2 = $_GET['num2']; 

    switch (true) {
    case !is_numeric($num1) && $operator == '/':
    case $num1 == '' && $operator == '/':
    case $num1 == '0' && $operator == '/':
        echo "ERRO: Numero 1 inserido e' zero";
        break;

    case !is_numeric($num2) && $operator == '/':
    case $num2 == '' && $operator == '/':
    case $num2 == '0' && $operator == '/':
        echo "ERRO: Numero 2 inserido e' zero";
        break;
    default:
        switch ($operator) {
            case '+':
                $result = $num1 + $num2;
                break;
            case '-':
                $result = $num1 - $num2;
                break;
            case '*':
                $result = $num1 * $num2;
                break;
            case '/':
                $result = $num1 / $num2;
                break;
        }
        echo "O resultado é: ".$result;
    }