Subgoals

Given the following code snippet, evaluate the final statement (the last line). If invalid, give the reason. If valid, what value is assigned to the variable? Note any possible side effects.

int alpha = 2, beta = 1, delta = 3, eta, gamma;
double omega = 2.5, theta = -1.3, kappa = 3.0, lambda, rho;

rho = beta + Math.pow(delta, alpha);

The expression is the right-hand-side (RHS) of the statement: beta + Math.pow(delta, alpha). Despite beta, delta, and alpha all being defined as int variables, we must check the API documentation for Math.pow to see what it returns.

In this official documentation, directly from Oracle, the left-hand column includes the return type, specified here as double.

Since beta is an int, it will be promoted when it is added to the double value returned by Math.pow, and the final result is a double value.

NOT USED IN THIS EXAMPLE

In Java, operands must be evaluated before operators, so Math.pow is called and returns before trying to add it to beta.

So, we start with Math.pow(3, 2), and we must again check the documentation to be sure we know which argument is which. The API doc says, “Returns the value of the first argument raised to the power of the second argument.” Thus, we use base 3 to the power of 2, which is 9. Since the API doc indicates a return type double, we should think of this value as 9.0.

Then we can add beta, so 1 + 9.0 gives us the final return value 10.0

The LHS is a variable of type double, and the RHS is type double. This is valid.

If we had tried to assign this value to an int variable, believing that all of the int operands would give us an int result, we would have had a compilation error for incompatible types. Ensuring compatible types is a common reason to check the API documentation for return types.

NOT USED IN THIS EXAMPLE