/**
* Evaluate a FunctionNode
*
* Computes the value of a FunctionNode `f(x)`, where f is
* an elementary function recognized by StdMathLexer and StdMathParser.
*
* @see \MathParser\Lexer\StdMathLexer StdMathLexer
* @see \MathParser\StdMathParser StdMathParser
* @throws UnknownFunctionException if the function respresented by the
* FunctionNode is *not* recognized.
*
* @param FunctionNode $node AST to be evaluated
* @retval float
*/
public function visitFunctionNode(FunctionNode $node)
{
$inner = $node->getOperand()->accept($this);
switch ($node->getName()) {
// Trigonometric functions
case 'sin':
case 'cos':
case 'tan':
case 'cot':
case 'arcsin':
case 'arccos':
case 'arctan':
case 'arccot':
case 'exp':
case 'log':
case 'lg':
case 'sinh':
case 'cosh':
case 'tanh':
case 'coth':
case 'arsinh':
case 'arcosh':
case 'artanh':
case 'arcoth':
throw new \UnexpectedValueException("Expecting rational expression");
case 'abs':
return new RationalNode(abs($inner->getNumerator()), $inner->getDenominator());
case 'sgn':
if ($inner->getNumerator() >= 0) {
return new RationalNode(1, 0);
} else {
return new RationalNode(-1, 0);
}
// Powers
// Powers
case 'sqrt':
return $this->rpow($inner, new RationalNode(1, 2));
case '!':
if ($inner->getDenominator() == 1 && $inner->getNumerator() >= 0) {
return new RationalNode(Math::Factorial($inner->getNumerator()), 1);
}
throw new \UnexpectedValueException("Expecting positive integer (factorial)");
case '!!':
if ($inner->getDenominator() == 1 && $inner->getNumerator() >= 0) {
return new RationalNode(Math::SemiFactorial($inner->getNumerator()), 1);
}
throw new \UnexpectedValueException("Expecting positive integer (factorial)");
default:
throw new UnknownFunctionException($node->getName());
}
}
public function testFactorial()
{
$this->assertEquals(1, Math::Factorial(0));
$this->assertEquals(6, Math::Factorial(3));
$this->assertEquals(362880, Math::Factorial(9));
}
