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May 6, 2020 05:16
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-module(recursion). | |
-export([fib/1,fibTail/1,pieces/2]). | |
-export([fibTest/0,fibTailTest/0,piecesTest/0]). | |
% Fibonaaci | |
fib(0) -> 0; | |
fib(1) -> 1; | |
fib(N) when N>1 -> | |
fib(N-2) + fib(N-1). | |
fibTest() -> | |
0 = fib(0), | |
1 = fib(1), | |
1 = fib(2), | |
2 = fib(3), | |
3 = fib(4), | |
5 = fib(5), | |
8 = fib(6), | |
13 = fib(7), | |
55 = fib(10), | |
passed. | |
% Tail recursive fibonacci | |
fibTail(N) -> fibTail(N, 0, 1). | |
fibTail(0, A, _) -> A; | |
fibTail(N, A, B) -> fibTail(N-1, A+B, A). | |
fibTailTest() -> | |
0 = fibTail(0), | |
1 = fibTail(1), | |
1 = fibTail(2), | |
2 = fibTail(3), | |
3 = fibTail(4), | |
5 = fibTail(5), | |
8 = fibTail(6), | |
13 = fibTail(7), | |
55 = fibTail(10), | |
passed. | |
% N cuts | |
% Reference: http://www.jlmartin.faculty.ku.edu/MiniCollege2012/handout.pdf | |
pieces(_,0) -> 1; | |
pieces(0,_) -> 1; | |
pieces(N, D) when N>=0, D>=1 -> | |
pieces(N-1,D-1) + pieces(N-1, D). | |
piecesTest() -> | |
% Dimension 0 | |
1 = pieces(0,0), % 0 cuts in dimension 0 | |
1 = pieces(1,0), % 1 cuts in dimension 0 ¯\_(ツ)_/¯ | |
% Dimension 1 | |
1 = pieces(0,1), | |
2 = pieces(1,1), | |
3 = pieces(2,1), | |
% Dimension 2 | |
1 = pieces(0,2), | |
2 = pieces(1,2), | |
4 = pieces(2,2), | |
7 = pieces(3,2), | |
11 = pieces(4,2), | |
% Dimension 3 | |
1 = pieces(0,3), | |
2 = pieces(1,3), | |
4 = pieces(2,3), | |
8 = pieces(3,3), | |
15 = pieces(4,3), | |
% Dimension 4 | |
1 = pieces(0,4), | |
2 = pieces(1,4), | |
4 = pieces(2,4), | |
8 = pieces(3,4), | |
16 = pieces(4,4), | |
31 = pieces(5,4), | |
passed. |
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Nice job!
Sytlistic tip: Erlang community (and tools, like eunit) tend to prefer using snake_case (i.e. pieces_test/0) over camelCase for function names, module names, and atoms in general.