Is it possible to match multiple parameters to a single function body? So for: def foo("a" = word) do word end def foo("b" = word) do word end def foo("c" = word) do "not a or b!" end have a single definition for the first two, so something like: def foo("a" = word) foo("b" = word) do …

Thank you all for the insight but the intent of my post wasn’t about the patterns themselves (they were just arbitrary examples) but how to write a function headers with arbitrary patterns for a single body. Given the responses, I’m assuming it’s not possible. Therefore I guess an answer is: def fo…

You can use a guard for that def foo(word) when word in [“a”, “b”] do end

What about in the more general pattern matching case? Ie if the pattern is not regular amongst the choices? def foo(["a", _] = list) foo([_,"b"] = list) do list end def foo(list) do "doesn't start with a or end with b!" end Is another helper function with multiple defns the way?

For a list starting with something, it’s trivial: def foo([first | _rest]) when first in ["a", "b"] do end For a list ending with something, it’s more involved as the Erlang lists are single-linked lists (in the C lingo) and you have to traverse the entire list to find the ending: def foo(list) w…

You are right but I want to add that if one has to check the last element more than once in a blue moon , maybe a list is not the correct data structure.

Keep in mind bar cannot be between the clauses of another function. It needs to be before or after.

FWIW, the common convention name for bar should be do_foo as well. To sum it all up: def foo("a") do: do_foo("a") def foo("b") do: do_foo("b") def foo(word) do "not a or b!" end defp do_foo(word) do word end

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Function Parameter Pattern Matching on multiple candidates?

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spammy April 5, 2026, 2:43pm 9

Perfect, thank you!