In some English accents, when you say "two for" quickly, it sounds like "two fer". Two-for-one is a way of saying that if you buy one, you also get one for free. So the phrase "two-fer" often implies a two-for-one offer.
Imagine a bakery that has a holiday offer where you can buy two cookies for the price of one ("two-fer one!"). You take the offer and (very generously) decide to give the extra cookie to someone else in the queue.
Your task is to determine what you will say as you give away the extra cookie.
If you know the person's name (e.g. if they're named Do-yun), then you will say:
One for Do-yun, one for me.
If you don't know the person's name, you will say you instead.
One for you, one for me.
Here are some examples:
| Name | Dialogue |
|---|---|
| Alice | One for Alice, one for me. |
| Bohdan | One for Bohdan, one for me. |
| One for you, one for me. | |
| Zaphod | One for Zaphod, one for me. |
One way to get optional arguments in scheme is by specifying the arguments as a list.
Two ways to do that are: (define (two-fer . args) ...) or (define two-fer (lambda args ...)).
Simply type make chez if you're using ChezScheme or make guile if you're using GNU Guile.
Sometimes the name for the scheme binary on your system will differ from the defaults.
When this is the case, you'll need to tell make by running make chez chez=your-chez-binary or make guile guile=your-guile-binary.
(load "test.scm") at the repl prompt.two-fer.scm reloading as you go.(test) to check your solution.If some of the test cases fail, you should see the failing input and the expected output.
The failing input is presented as a list because the tests call your solution by (apply two-fer input-list).
To learn more about apply see The Scheme Programming Language -- Chapter 5
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