Question

This is the code that I have to refactor for my homework:

if (state == TEXAS) {
    rate = TX_RATE;
    amt = base * TX_RATE;
    calc = 2 * basis(amt) + extra(amt) * 1.05;
} else if ((state == OHIO) || (state == MAINE)) {
    rate = (state == OHIO) ? OH_RATE : MN_RATE;
    amt = base * rate;
    calc = 2 * basis(amt) + extra(amt) * 1.05;
    if (state == OHIO)
        points = 2;
} else {
    rate = 1;
    amt = base;
    calc = 2 * basis(amt) + extra(amt) * 1.05;
}

I have done something like this

if (state == TEXAS) {
    rate = TX_RATE;
    calculation(rate);
} 
else if ((state == OHIO) || (state == MAINE))
    {
rate = (state == OHIO) ? OH_RATE : MN_RATE;

calculation(rate);

if (state == OHIO)
    points = 2;
}

else {
    rate = 1;
    calculation(rate);
}

function calculation(rate)
{
    amt = base * rate;
    calc = 2 * basis(amt) + extra(amt) * 1.05;
}

How could I have done better?
Edit i have done code edit
amt = base * rate;

Answer 1

Steve’s point about the switch statement is a good one, but I’d like to suggest a different approach: arrays.

If you store the rate information in an array and index into it by state, you can make maintaining this sort of code easier in the long term.

Consider this:

#define OTHER 0
#define OHIO 1
#define MAINE 2
#define TEXAS 3

int rates[4];
rates[OTHER] = ...
rates[OHIO] = ...
rates[MAINE] = ...
rates[TEXAS] = ...

See what this might let a calculate function do differently. (Note that in “real life”, the int rates[4] array could be done many different ways — a hashmap, a simple array of struct rate { char state[12]; int rate; } objects with state names and rates stored together at runtime, or a simple statically-assigned array int rates[4] = {0, 2, 3, 10};. I chose this because it shows indexing the array by #defined content. enum also works.)