I have this helper function where I exploit the Errors in Guards feature. def non_empty(val, _msg) when length(val) > 0, do: {:ok, val} def non_empty(val, _msg) when map_size(val) > 0, do: {:ok, val} def non_empty(val, _msg) when tuple_size(val) > 0, do: {:ok, val} def non_empty(_val, msg), do: {:e…

This is how I would rewrite your clauses into just two. def non_empty(val, _msg) when is_list(val) and val != [] when is_map(val) and map_size(val) > 0 when is_tuple(val) and tuple_size(val) > 0 do {:ok, val} end def non_empty(_val, msg), do: {:error, msg} by checking …

size is constant time O(1), where as length is linear time -O(N) - Naming conventions — Elixir v1.20.2 Isn’t non_empty for lists a bit more expensive operation - depending on size of list? Enum.empty?/1 just compares to when it is list. def empty?(enumerable) when is_list(enumerable) do enu…

[image] kartheek: def non_empty([], msg), do: {:error, msg} def non_empty({}, msg), do: {:error, msg} def non_empty(%{} = val, msg) when map_size(val) == 0, do: {:error, msg} def non_empty(val, _msg), do: {:ok, val} please don’t! It totally changes the logic of the function, unless yo…

[image] Sebb: (I can call non_empty({:foo}, "") though length({:foo}) raises) Is there a way to put this into a defguard - without using is_list/1 etc? Why don’t you want to use is_list/1 and what is the issue with raising within the guard?

or you can make it a guard, it will not work for structs though. defguard is_non_empty(term) when (is_list(term) and term != []) or (is_map(term) and map_size(term) > 0) or (is_tuple(term) and tuple_size(term) > 0)

[image] Sebb: Is there a way to put this into a defguard - without using is_list/1 etc? non_empty function using defguards: defguard is_non_empty(enum) when ((enum == []) or (enum == {}) or (is_map(enum) and map_size(enum) == 0)) == false def non_empty(val, _msg) when is_non_empty(val), d…

[image] kartheek: defguard is_non_empty(enum) when ((enum == []) or (enum == {}) or (is_map(enum) and map_size(enum) == 0)) == false @kartheek , that is definitely the solution to the question by the OP

@eksperimental I feel both our solutions are very similar. Fun collaborating with you. @Sebb I was running some benchmarking (just for fun) for below data. Your existing version was taking hit when data is non empty list. You may have to change it. Which version to use ? you have to figure out by…

[image] kartheek: @eksperimental I feel both our solutions are very similar. Fun collaborating with you. @kartheek definitely yours is more performant. Here’s another version I think even simpler, that builds on your idea. defguard is_non_empty(term) when term not in [{}, [], %{}]

[image] eksperimental: Here’s another version I think even simpler, that builds on your idea. This is simpler :+1: This will be slower than your original defguard. [image] eksperimental: @kartheek definitely yours is more performant. As long as time complexity of expression is constan…

Wow, I am surprised by the result, it could be that is_list(term) is faster than term == [], and so on with the other is_* functions. We could benchmark these. The other thing is that it is so fast than the results are imprecise. If the results are correct, then it pays off to always check for th…

Exploit "Errors in guards" in defguard

Questions & Help Questions

eksperimental January 22, 2022, 2:46pm 5

Why don’t you want to use is_list/1 and what is the issue with raising within the guard?