oliveiragahenrique
I’m current learning Elixir by the book Elixir in Action 2nd Edition. On chapter 3 at Stream functions exercises i’ve solved them a bit different from the original repository.
Problem: Get the longest line length of a file
Book resoluiton:
def longest_line_length!(path) do
path
|> Stream.map(&String.replace(&1, "\n", ""))
|> Stream.map(&String.length/1)
|> Enum.max()
end
My resolution:
def longest_line_length!(path) do
File.stream!(path)
|> Stream.map(&String.replace(&1, "\n", ""))
|> Stream.map(&String.length(&1))
|> Enum.max()
end
Is there some fundamental difference between Stream.map(&String.length/1) and Stream.map(&String.length(&1)) ?
Or it is just a style preference?
Personally I think it’s more clear to use &1 even if it’s not necessary. Maybe it is just because I’m still getting used with the language. Any thoughts?
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srowley
I had the same reaction and preference when I first started learning Elixir. There may be some real difference between them that I am not aware of; I just think of it as a style difference.
Over time as I got accustomed to referring to a function as
Module.function/arity, the former syntax (i.e.&String.length/1) became more natural and the latter started to feel redundant/unnecessary.i-n-g-m-a-r
2 calls vs 1
oliveiragahenrique
Hmmm… can you explain a bit more? I’m learning yet.
I did not get how the
&String.length(&1)is called twice, why is this so?NobbZ
It’s not that that function is called twice, but it causes two function calls.
Using
&f(&1)needs to first call the anonymous function which calls then the inner function call. Using&f/1creates a more direct “reference” to the target function and therefore removes one level of indirection.Marcus
But something like this will be optimised by the compiler.
For example:
becomes
But
&String.upcase/1should be the preferred form.shanesveller
Besides the points above, if you’re not reordering or transforming arguments before calling the existing function, the
Mod.fun/aritystyle is more succinct to read and write, especially for functions with arity > 1.fun(&1, &2, &3)is repetitive in a way that isn’t productive.