2. Funs

2 Funs

2.1 map

The following function, double, doubles every element in a list:

double([H|T]) -> [2*H|double(T)];
double([])    -> [].

Hence, the argument entered as input is doubled as follows:

> double([1,2,3,4]).
[2,4,6,8]

The following function, add_one, adds one to every element in a list:

add_one([H|T]) -> [H+1|add_one(T)];
add_one([])    -> [].

The functions double and add_one have a similar structure. This can be used by writing a function map that expresses this similarity:

map(F, [H|T]) -> [F(H)|map(F, T)];
map(F, [])    -> [].

The functions double and add_one ca