Elixir:十进制转换，不允许使用负数

defmodule Conversion do
  def decimal_to_base(decimal, base) when base in 2..36 do
    if decimal < 0 do
      {:error, "Decimal number cannot be negative"}
    else
      do_conversion(decimal, base)
    end
  end

  defp do_conversion(decimal, base) do
    if decimal < base do
      [to_char(decimal)]
    else
      remainder = decimal rem base
      do_conversion(decimal div base, base) ++ [to_char(remainder)]
    end
  end

  defp to_char(number) when number < 10 do
    Integer.to_string(number)
  end

  defp to_char(number) do
    String.upcase(Integer.to_string(number + 55))
  end
end

Conversion.decimal_to_base(42, 2)  # 将十进制数 42 转换为二进制
Conversion.decimal_to_base(42, 8)  # 将十进制数 42 转换为八进制
Conversion.decimal_to_base(42, 16) # 将十进制数 42 转换为十六进制