Web Development with ReasonML

Doing Conditional Computation

Let’s add a bit of complexity to our price calculator: discounts. If you order fewer than ten items, you get a 5% discount. Otherwise, you get a 10% discount. We want the program to:

1. Calculate the total price.

2. Calculate the appropriate discount rate.

3. Calculate the cost with and without discount.

4. Print both, properly labeled.

Step 2 requires us to use an if/else expression:

first-project/src/DiscountPrice.re

let discount =
  if (qty < 10) {
    0.05;
  } else {
    0.10;
  };

In ReasonML, the if keyword introduces an expression, not a statement. This crucial difference means you can bind the result of an if expression to a variable. It also means you must provide an else clause, and the results of both ...