Question

I have started some hands on in Erlang and I am getting : ** 1: syntax error before: '->' ** whenever i am declaring any function for eg. to calculate sum of a list (this is experimental, of cource there is Built In Function for find sum of a list).

sum([]) -> 0;
sum([H | T]) -> H + sum(T).

in erl shell (v 5.5.5).

Thanks in advance

Answer 1

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.