PHP coding

[wisni1rr]

I am building a calculator program to help learn PHP. In the following example, I wrote a function to calculate exponents. When I run this function, It always takes the first case.

function power_of($base, $exponent)
{
	$result = $base;
	switch ($exponent)
	{
		case $exponent = 0:
			$result = 1;
			break;
		case  $exponent > 1:
			while ($exponent > 1)
				{
				$result = $result * $base;
				$exponent--;
				}
			break;
		case  $exponent < -1:
			while ($exponent < -1)
				{
				$result = $result * $base;
				$exponent++;
				}
			$result = 1 / $result;
			break;	
	}
	return $result;
}

Any Ideas why that is?

[brettl]

What is the value of $exponent? If it has no value it may be validating it as false that's why only the first case will work.

[Rabbit]

= is an assignment operator. == is a comparison operator.

[wisni1rr]

Thanks, brettl & Rabbit.

$exponent and $base are retrieved from $_POST().

I added {==} to Line 6 of the code in post #1.

If I enter 500 for $base and 0 for $exponent, I get the $result of 500.

[Rabbit]

That will depend on how you're calling the function.

[macoy23]

The 1st case should be $exponent == 0: NOT $exponent =0:

[wisni1rr]

The function is called in this statement:

	switch ($operator)
	{
		case 'add':
			$result = $input1 + $input2;
			break;
		case 'sub':
			$result = $input1 - $input2;
			break;
		case 'mult':
			$result = $input1 * $input2;
			break;
		case 'idiv':
			$result = $input1 / $input2;
			$result = (integer)$result;
			break;
		case 'div':
			$result = $input1 / $input2;
			break;
		case 'modulus':
			$result = $input1 % $input2;
			break;
		case 'sqrt' :
			$result = babylonian_square_root($input1);
			break;
		case 'power_of' :
			$result = power_of($input1, $input2);
			break;
		case 'factorial' :
			$result = factorial($input1);
			break;
		
		default:
			$result = INVALID_OPERATOR;
			break;
	}
	if ($radix == 'hex')
	{
		$result = decimal_to_hex($result, true);
		$start_again_radix = '?hex';
	}
}	
else 
	$result = INVALID_INPUT;

$operator $input1 $input2 are all $_POST from another php file.

I changed line 6 in P1 to:

$exponent == 0

Still does not take the branch it should.

[wisni1rr]

The function is called in this statement:

	switch ($operator)
	{
		case 'add':
			$result = $input1 + $input2;
			break;
		case 'sub':
			$result = $input1 - $input2;
			break;
		case 'mult':
			$result = $input1 * $input2;
			break;
		case 'idiv':
			$result = $input1 / $input2;
			$result = (integer)$result;
			break;
		case 'div':
			$result = $input1 / $input2;
			break;
		case 'modulus':
			$result = $input1 % $input2;
			break;
		case 'sqrt' :
			$result = babylonian_square_root($input1);
			break;
		case 'power_of' :
			$result = power_of($input1, $input2);
			break;
		case 'factorial' :
			$result = factorial($input1);
			break;
		
		default:
			$result = INVALID_OPERATOR;
			break;
	}
	if ($radix == 'hex')
	{
		$result = decimal_to_hex($result, true);
		$start_again_radix = '?hex';
	}
}	
else 
	$result = INVALID_INPUT;

$operator $input1 $input2 are all $_POST from another php file.

I changed line 6 in P1 to:

case $exponent == 0:

Still does not take the branch it should.

[Rabbit]

I would output the values to double check that the correct values are getting passed.