Week 1 assignment kent university functional programming in erlang

assignment.erl

-module(assignment).

-export([perimeter/1,area/1,enclose/1,bits/1]).

perimeter({square,R}) ->
    4 * R;
perimeter({triangle,A,B,C}) ->
    A + B + C;
perimeter({circle,R}) ->
    2 * math:pi() * R .

area({circle,R}) ->
    math:pi() *R*R;
area({rectangle, Length, Width}) -> 
    Length * Width;
area({triangle, A, B, C}) ->
  S = (A + B + C) / 2,
  math:sqrt(S * (S - A) * (S - B) * (S - C)).

enclose({circle, R}) ->
  {rectangle, R * 2, R * 2};

enclose({rectangle, W, H}) ->
  {rectangle, W, H};

enclose(T = {triangle, A, B, C}) ->
  Area = area(T),
  Base = max(max(A, B), max(B, C)),
  Height = (Area * 2) / Base,
  {rectangle, Base, Height}.

bits(V) ->
    bits(V, 0).
bits(0, C) ->
    C;
bits(V, C) ->
    bits( (V band (V - 1)), (C + 1)).