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| 1 | +CREATE OR REPLACE FUNCTION public.negafibonacci_sequence(total int) |
| 2 | + returns setof int |
| 3 | + immutable |
| 4 | + strict -- returns null if any parameter is null |
| 5 | + parallel safe -- Postgres 10 or later |
| 6 | + security invoker |
| 7 | + language plpgsql |
| 8 | + set search_path = '' |
| 9 | +AS |
| 10 | +$func$ |
| 11 | +DECLARE |
| 12 | + a int := 0; |
| 13 | + b int := 1; |
| 14 | + |
| 15 | + i int := 2; |
| 16 | + min_total int := 3; |
| 17 | + max_total int := 47; |
| 18 | +BEGIN |
| 19 | + --inspired by: https://stackoverflow.com/questions/75588188/generating-fibonacci-sequence-with-pl-pgsql-function |
| 20 | + |
| 21 | + IF total NOT BETWEEN min_total AND max_total THEN |
| 22 | + RAISE EXCEPTION 'First parameter betwen % and % expected, % given', min_total, max_total, total; |
| 23 | + END IF; |
| 24 | + |
| 25 | + RETURN NEXT 0; |
| 26 | + RETURN NEXT 1; |
| 27 | + LOOP |
| 28 | + i := i + 1; |
| 29 | + a := a - b; |
| 30 | + RETURN NEXT a; |
| 31 | + EXIT WHEN i = total; |
| 32 | + |
| 33 | + i := i + 1; |
| 34 | + b := b - a; |
| 35 | + RETURN NEXT b; |
| 36 | + EXIT WHEN i = total; |
| 37 | + END LOOP; |
| 38 | +END; |
| 39 | +$func$; |
| 40 | + |
| 41 | +comment on function public.negafibonacci_sequence(total int) is $$ |
| 42 | + Generates negative Fibonacci sequence. |
| 43 | +$$; |
| 44 | + |
| 45 | + |
| 46 | +--TEST |
| 47 | +do $$ |
| 48 | + begin |
| 49 | + assert (select count(*) = 32 and sum(v) = 832041 and max(v) = 1346269 |
| 50 | + from public.negafibonacci_sequence(32) with ordinality as t(v, o) |
| 51 | + ); |
| 52 | + end; |
| 53 | +$$; |
| 54 | + |
| 55 | +--select array(select public.negafibonacci_sequence(32)); |
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