/case-vs-multiple-clause-function

Primary LanguageElixir

Do case and multiple clause functions compile to the same VM instructions?

Answer: yes.

Proof

I'm creating two modules, both implement a my_test_function function that only differs between the two modules with one detail: one implementation uses a case expression, and the other multiple clause functions.

Compiling

$ elixirc test1.ex
$ elixirc test2.ex

Decompiling

file1 = File.read!("./Elixir.Test1.beam")
decompiled1 = :beam_disasm.file(file1)
File.write!("./decompiled1.ex", Macro.to_string(decompiled1))

file2 = File.read!("./Elixir.Test2.beam")
decompiled2 = :beam_disasm.file(file2)
File.write!("./decompiled2.ex", Macro.to_string(decompiled2))

Format decompiled files:

$ mix format decompiled1.ex
$ mix format decompiled2.ex

Diff

After compiling the two modules to BEAM files and then decompiling, the implementations of the two functions are identical. Thus is it my conclusion that case and multiple clause functions are equivalent after compiling.