Just trying to do simple sum of list values.
defmodule Mth do
def sum_list([]) do
0
end
def sum_list([H|T]) do
H + sum_list(T)
end
end
IO.puts Mth.sum_list([1, 2, 300])
But I get this error:
**(FunctionClauseError) no function clause matching in Mth.sum_list/1
pokus.ex:3: Mth.sum_list([1, 2, 300])
pokus.ex:14: (file)
(elixir) src/elixir_lexical.erl:17: :elixir_lexical.run/2
(elixir) lib/code.ex:316: Code.require_file/2**
You need to use lowercase letters for variable and functions names. Identifiers starting with uppercase are reserved for modules:
defmodule Mth do
def sum_list([]) do
0
end
def sum_list([h|t]) do
h + sum_list(t)
end
end
iex> IO.puts Mth.sum_list([1, 2, 300])
303
:ok
h + sum_list(t) would be executed as follows 1. sum_list(t) 2. h + So the last function call here would be the +. This would mean that if you had a very long list you could get a stack overflow error. Somewhat ironic, I know.To improve upon Chris's solution, if you want your sum function to be tail recursive, you'd need to modify it a bit to be:
defmodule Mth do
def sum_list(list), do: do_sum_list(list, 0)
defp do_sum_list([], acc), do: acc
defp do_sum_list([h|t], acc), do: do_sum_list(t, acc + h)
end
iex> Mth.sum_list([1, 2, 300])
303
If you are going to use Enum.reduce you can go simpler:
defmodule Mth do
def sum_list(list), do: Enum.reduce(list, 0, &(&1 + &2))
end
def sum_list(list), do: Enum.reduce(list, 0, &Kernel.+/2) this also works ;)Just for sake of completeness this would also work:
defmodule Mth do
def sum_list(list), do: do_sum_list(list,0)
defp do_sum_list(l,i_acc), do: Enum.reduce(l, i_acc, fn(x, accum) -> x + accum end)
end
I post this solely for reference for others who may find this question and it's answers.
Try this:
sum_list=[1,2,300]
Enum.sum sum_list
303
