I’m trying to take a float, add it to the array of floats in a model instance, and save it back to the database. I only want the array to have a max length of 90. Here is my code for that so far. def add_price(model, %{"price" => price}) do current_price = model.price price_list = ca…

You cannot run length/1 inside a pattern match. You should move it to a guard: list when length(list) < 90 -> [list | price]

Because only a limited set of functions is callable in a guard, those are called guardsafe functions. This is a limitation of the BEAM to make some optimisations possible. Basically it is, because the BEAM weren’t allowed to reorder clauses if functions in a guard were allowed to have side effects. …

Elixir Programming Language Forum

Cannot invoke remote function :erlang.length/1 inside match

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DIW October 24, 2017, 5:19am 3

Thanks! That worked