The cast Operator

Recall the definition of the operators we have seen.

Note that division is defined to be integer division when both operands are integers. In our program, both numerator and denominator are declared to be integers, so the result of the division is also an integer. With integer division, 3/8 is 0. This we get the price to be 11.0000.

How do we fix it?

We could change the types of the numerator and/or denominator to be float, but the meaning of these variables is inherently integer, we should leave them that way.

What we would like to do is just change the type of these values for the purpose of this calculation only. C provides an operator to do just that: the cast operator. The syntax is:

     ( <type identifier> ) <variable name>

which we can use anywhere in any expression. This cast expression DOES NOT change the type of cell used to store the variable, nor does it change the value stored in that cell. Instead, it accesses the value in the cell, and converts it to the requested type to use in the expression.

So, the calculation of price becomes:

        price = (sell_whole + (float)sell_numer / (float)sell_denomin);

When we modify the code, compile it, and run it, we get the output:

You have 57 shares of XYZ Corp.
selling at $ 11 3/8
degug: price = 11.375000

The value of the stock is $648.375000

The price is calculated correctly, and we get the correct answer for the portfolio value. We can then fix the original assignment statement:

        /*  Calculate  portfolio  value  */
        portfolio_value = shares * (sell_whole +
                (float)sell_numer / (float)sell_denomin);

and remove the debugging code we inserted (or just comment it out, in case we need to use it again later - we will see better ways to do this soon).

to Overview.