Answer by Daniel Luna for Erlang getting error ** 1: syntax error before: '->' **

You can't define functions in the shell using the same syntax as in an erl file.

You can define fun's though.

Syntax in the shell needs to be:

Sum = fun([], _) -> 0; ([H | T], F) -> H + F(T, F) end,
Sum([1,2,3], Sum).

Note that recursive anonymous functions (which this is) are defined in an ugly way. You basically have to pass the function as an argument to itself.