a26.erl

% Marcelo Ruiz Camauër
% assignment 2.6

-module(a26).
-export([listprod/1,listprod2/1,listmax/1,listmax2/1]).

% define an Erlang function to give the product of a list of numbers. 
% The product of an empty list is usually taken to be 1

% recursive listprod():
listprod([])  ->  1;
listprod([H|T]) -> H * listprod(T).


% Define an Erlang function to give the maximum of a list of numbers.
% tail recursive listmax():
listmax(L) when L /= []  -> listmax(tl(L),hd(L)).  % only valid for non-empty lists!
listmax([],_Item) -> _Item;  % when no more items in list we have the max item.
listmax([H|T],Maxitem) -> listmax(T,max(H,Maxitem)). % keep the max item, recurse on the rest of the list.


% In each case you could give either a direct recursion or a tail recursive definition. 
% Give the other kind of definition for product and maximum.

% tail recursive listprod():
listprod2([])  ->  1;
listprod2([H|T]) -> listprod2(T,H).
listprod2([],Acc) -> Acc;
listprod2([H|T],Acc) -> listprod2(T,H * Acc).


% recursive listmax():
listmax2([L]) when L/=[] -> L;
listmax2([H|T]) -> (max(H,listmax2(T))). % keep the max item, recurse on the rest of the list.