I’d say both select an item. So they’re doing the same job. Just some inputs might recurse a few more times than others to get to an answer.
LostKobrakai
NobbZ
As @LostKobrakai already pointed out, both do the same thing. They select the item from the list of items.
The multiheaded function you see there, has nothing to do with “differentiating functions by arity”, in fact, nothing is differentiated there, both are the same function, as both have the same name and the same arity.
What though I do use there is “pattern matching”, something very important to learn and understand when writing elixir.
To be honest, those 2 function clauses are semantically equivalent with the following single-clause function:
defp select_item(items, idx) do
case items do
[{name, weight}|_] when idx < weight -> name
[{_, weight} | tail] -> select_item(tail, idx - weight)
end
end
But it is idiomatic to move such a case which matches on an argument directly and spans the full function body into a multi clause function.
Also in general pattern matching in the functions head or a case is usually prefered of using if and some predicate functions and/or using getter functions.
2
LostKobrakai
Not only semantically. Afaik the compiler does take functions with many function heads and makes them be a single function with a case statement inside.
0
NobbZ
I’m not sure if elixir does this already, but yes, at least for the core-erlang representation it is necessary to do so, as core erlang only has single clause functions IIRC.
0
peerreynders
Pattern matching‡ is the conditional construct - the case expression is just one way of utilizing it.
‡ Not to be confused with destructuring:
Kernel.destructure/2- JavaScript destructuring assignment
2
