function fibonacci

Author: rin-nas

functions/fibonacci.sql

@@ -0,0 +1,41 @@
+CREATE OR REPLACE FUNCTION fibonacci(pstop int = 10)
+  RETURNS SETOF int
+  LANGUAGE plpgsql IMMUTABLE STRICT AS
+$func$
+DECLARE
+    a int := 0;
+    b int := 1;
+BEGIN
+   -- optional sanity check:
+   -- function starts operating at 2
+   -- and int4 computation overflows past Fibonacci Nr. 1836311903
+   IF pstop NOT BETWEEN 2 AND 1836311903 THEN
+      RAISE EXCEPTION 'Pass integer betwen 2 and 1836311903. Received %', pstop;
+   END IF;
+
+   RETURN NEXT 0;
+   RETURN NEXT 1;
+   LOOP
+      a := a + b;
+      EXIT WHEN a >= pstop;
+      RETURN NEXT a;
+
+      b := b + a;
+      EXIT WHEN b >= pstop;
+      RETURN NEXT b;
+   END LOOP;
+END;
+$func$;
+--source: https://stackoverflow.com/questions/75588188/generating-fibonacci-sequence-with-pl-pgsql-function
+
+comment on function fibonacci(pstop int) is 'Generates Fibonacci sequence';
+
+--TEST
+do $$
+    begin
+        assert (select count(*) = 32 and sum(i) = 3524577
+                from fibonacci(1346270) as t(i)
+               );
+    end;
+$$;
+