Put all in toguether1

pat.erl

-module(pat).

-export([perimeter/1,area/1,enclosure/1,bits/1,bits_rec/1,tests/0]).

%Shapes exercises
%I considered not necessary to validate the shapes as john don't use it during his examples,
% forexp in circle R > 0 and in triangle A + B > C,etc..

perimeter({circle,_,Radius}) ->
	2 * math:pi() * Radius;
perimeter({rectangle,_,H,W}) ->
        (2 * H) + (2 * W);
perimeter({triangle,_,A,B,C}) ->
        A + B + C.


area({circle,_,Radius}) ->
	math:pi() * Radius * Radius;
area({rectangle,_,H,W}) ->
        H * W;
%triangle area from Herón formula, explained in week one.
area({triangle,_,A,B,C}) ->
	S = (A+B+C)/2,
	math:sqrt(S*(S-A)*(S-B)*(S-C)).


enclosure({circle,{X,Y},Radius}) ->
	Diameter=2*Radius,
	{rectangle,{X,Y},Diameter, Diameter};
%Triangle heigh from Herón formula also.
enclosure({triangle,{X,Y},A,B,C}) ->
	Ha = (2/A)*area({triangle,{X,Y},A,B,C}),
	{rectangle,{X,Y},A,Ha}.


%%%%%
bits(X) -> 
	bits_tail(X,0).

%bits tail recursive func:
bits_tail(0,Acc) -> 
	Acc;
bits_tail(X,Acc) -> 
	bits_tail(X div 2,Acc + (X rem 2)).

%bits recursive func:
bits_rec(0) -> 
	0;
bits_rec(X) -> 
	X rem 2 +  bits_rec(X div 2).



tests() ->
     18.84955592153876 = perimeter({circle,{0,0},3}),
     18 = perimeter({rectangle,{0,0},3,6}),
     15 = perimeter({triangle,{0,0},4,5,6}),
     28.274333882308138 = area({circle,{0,0},3}),
     18 = area({rectangle,{0,0},3,6}),
     1 = bits(8),
     3 = bits(7),
     1 = bits_rec(8),
     3 = bits_rec(7),
     success.