Hi, I am wondering why my solution wil not work 1. source: Perfect Numbers in Elixir on Exercism 2. solution attempt: @spec classify(number :: integer) :: {:ok, atom} | {:error, String.t()} def classify(number) do case aliquot_sum(number) do number -> ok(:perfect) x when x > nu…

The first case clause matches any number. The clauses’ order matters.

But I used the same variable name in function clause, so I would expect that It would match against it

Oh, I get you now. You can use the pin operator ^number.

No, your logic is wrong and number might not be what You think… As soon as there is a match, the rest of the case is discarded [image] przemyxe0p: case aliquot_sum(number) do number -> ok(:perfect) # <- THE NUMBER HERE MATCH ANYTHING x when x > number -> ok(:abundant) x when…

After adding ^ operator it’s right why should I use cond? What is more “idiomatic” whatever this “idiomatic” word mean? :smiley:

Because it’s very rare to use ^number in the case :slight_smile: Yet, You can do as You like

Last question, i cannot find explanatio why this works that way. Do you have explanation or link to resources?

Pattern matching — Elixir v1.20.2

People have a weird aversion to cond for some reason that I don’t really understand. Doing pure boolean checks is exactly what it exists for. The case version is essentially the same with unnecessary extra syntax. Using cond gives added information that indeed all clauses are boolean checks. It’…

Elixir Programming Language Forum

Scope of variable passed to function

Questions & Help Questions

krasenyp March 1, 2025, 10:58am 8

In my experience it’s very rare to use cond but it’s still valid.