Elixirで変数の型名を文字列として取得する。iexインタプリタのiコマンドみたいなことがしたかった。
defmodule Typename do @spec get(any) :: String.t() def get(x) do dict = %{ &is_atom/1 => "atom type", &is_binary/1 => "binary type", &is_bitstring/1 => "bitstring type", &is_boolean/1 => "boolean type", &is_float/1 => "float type", &is_function/1 => "function type", &is_integer/1 => "integer type", &is_list/1 => "list type", &is_map/1 => "map type", &is_number/1 => "number type", &is_pid/1 => "pid type", &is_reference/1 => "reference type", &is_tuple/1 => "tuple type", } typename_list = Enum.filter_map( dict, fn {pred, _} -> pred.(x) end, fn {_, name} -> name end) if Enum.empty?(typename_list) do "unknown type" else Enum.join(typename_list, " && ") end end end x = "hello" IO.puts "x type is #{Typename.get(x)}"
出力：
x type is binary type && bitstring type
