imported>WikiSysop v 22. 2. 2007, 12:49

2007-02-22T12:49:25Z

Nová stránka

<pre>
DROP SCHEMA fractal CASCADE;

CREATE SCHEMA fractal;

CREATE TABLE fractal.disp (
id INT PRIMARY KEY,
content VARCHAR(1000)
);

CREATE TABLE fractal.shade (
id INT PRIMARY KEY,
value INT
);

CREATE FUNCTION ord(text) RETURNS int AS $$SELECT ascii($1); $$ LANGUAGE SQL IMMUTABLE; -- <nove>
CREATE FUNCTION concat(text, text) RETURNS text AS $$ SELECT $1 || $2; $$ LANGUAGE SQL IMMUTABLE; -- <nove>

INSERT INTO fractal.shade (id,value) VALUES (0,ORD(' ')),(1,ORD('.')),(2,ORD(',')),(3,ORD('-')),(4,ORD('~')),
(5,ORD('*')),(6,ORD(':')),(7,ORD(';')),(8,ORD('+')),
(9,ORD('o')),(10,ORD('O')),(11,ORD('&')),(12,ORD('%')),(13,ORD('@'));

CREATE OR REPLACE FUNCTION fractal.mandelbrot (IN x_max INT, IN y_max INT, OUT _content VARCHAR(1000)) -- <zm>
RETURNS SETOF VARCHAR(1000) AS $$ -- <nove>
BEGIN
DECLARE x INT DEFAULT 0;
DECLARE y INT DEFAULT 0;
DECLARE xf0 FLOAT;
DECLARE yf0 FLOAT;
DECLARE xf1 FLOAT;
DECLARE yf1 FLOAT;
DECLARE tf FLOAT;
DECLARE l INT;
DECLARE l_max INT;
DECLARE buffer VARCHAR(1000);
DECLARE tint INT;
TRUNCATE fractal.disp; -- <zm>
SET l_max = (SELECT MAX(id) FROM fractal.shade LIMIT 1); -- <zm>
WHILE y<y_max DO
SET buffer='';
SET x=0;
WHILE x<x_max DO
SET xf0=x*4.0/x_max-2.0;
SET yf0=y*4.0/y_max-2.0;
SET xf1=xf0;
SET yf1=yf0;
SET l=0;
WHILE l<l_max AND xf1*xf1+yf1*yf1<4.0 DO
SET tf=xf1*xf1-yf1*yf1+xf0;
SET yf1=2.0*xf1*yf1+yf0;
SET xf1=tf;
SET l=l+1;
END WHILE;
SET tint = (SELECT value FROM fractal.shade WHERE id=l); -- <zm>
SET buffer=CONCAT(chr(tint),buffer); --<zm>
SET x=x+1;
END WHILE;
INSERT INTO fractal.disp (id,content) VALUES (y,buffer); -- <zm>
SET y=y+1;
END WHILE;
RETURN (SELECT content FROM fractal.disp ORDER BY id ASC); -- <zm>
END;
$$ LANGUAGE plpgpsm;

SELECT * FROM fractal.mandelbrot (50,30); -- <zm>
</pre>

Zdrojový kód procedury generující fraktál pro PostgreSQL - Historie editací

imported>WikiSysop v 22. 2. 2007, 12:49