Erlang String Operations

rna_transcribe.erl

%% So Dna will be a string like "ABCDEFG"
%% and Erlang treats it like a list, but when you get the Head of the list
%% it's not like a regular String like I'm used to, so to pattern match it I used the $ thing.
%% Not sure what $ is called but it works to match when we get the character "G" from Dna.
%% Fall through needs to convert the binary form back to a list
%% So it looks like a String.
%% that's my explanation...

%%Dna = "ABCDEFG"
rna(Dna) ->
  lists:concat(lists:map(fun(Strand) -> rna_transcribe(Strand) end, Dna)).

% When we reach "G", this will match
rna_transcribe($G) -> "C";

%% Everything else falls through, if we don't use binary_to_list we would just get an integer representation
%% Just an Erlang thing.
rna_transcribe(Strand) -> binary_to_list(<<Strand>>).