public function __construct($symbol = null)
{
$this->symbol = $symbol;
$this->environment = Environment::getInstance();
$this->traversable = null;
$this->forAll = null;
}
public function m($symbolOne, $symbolTwo)
{
$operandOne = Environment::getInstance()->resolve($symbolOne);
if (is_int($symbolTwo) || is_float($symbolTwo)) {
$operandTwo = $symbolTwo;
} else {
$operandTwo = Environment::getInstance()->resolve($symbolTwo);
}
// Make sure operandOne is an int or a float
if (!is_int($operandOne) && !is_float($operandOne)) {
throw new \InvalidArgumentException("The value for symbol '{$symbolOne}' is neither an int nor a float.");
}
// Make sure operandTwo is an int or a float
if (!is_int($operandTwo) && !is_float($operandTwo)) {
throw new \InvalidArgumentException("The value for symbol '{$symbolTwo}' is neither an int nor a float.");
}
$result = $operandOne - $operandTwo;
$this->setOperand("__x__", $result);
}
/**
* Test the getInstance method
*
* This method must return the same instance of the Environment class
*/
public function testGetInstance()
{
$environmentTwo = Environment::getInstance();
$this->assertSame($this->environment, $environmentTwo, "Failed to assert that the getInstance method returns the same environment. The environment must be a singleton.");
}
public function be($value)
{
Environment::getInstance()->attach($this->symbol, $value);
}