Programmer Passport: Elixir

Using Maps in Bulk

Let’s build a program to create all of the Roman numeral values from 1 to 1000. We could do so by adding a number to a map, one at a time, but that’s not a functional design.

There’s a better way, though. When you can, it’s better to think more broadly. When you’re building a big, predictable map, don’t build it one piece at a time. Build all of the tuples at once, and then dump them all at once into a new map.

Let’s take an example. Create a new mix project called Romans, like this:

[elixir] ➔ mix new roman
...
[elixir] ➔ cd roman
[roman] ➔

Now, let’s think a bit. We’ll want to build a function to calculate the first Roman digit from the left, given a decimal number. The code will look like this:

def digit(number) ...