/* The mandelbrot set */
WITH RECURSIVE Z(IX, IY, CX, CY, X, Y, I) AS (
SELECT IX, IY, X::float, Y::float, X::float, Y::float, 0 FROM (select -2.2 + 0.031 * i, i from generate_series(0,101) as i) as xgen(x,ix), (select -1.5 + 0.031 * i, i from generate_series(0,101) as i) as ygen(y,iy) UNION ALL SELECT IX, IY, CX, CY, X * X - Y * Y + CX AS X, Y * X * 2 + CY, I + 1 FROM Z WHERE X * X + Y * Y < 16::float AND I < 100 )
SELECT array_to_string(array_agg(SUBSTRING(' .,,,—–++++%%%%@@@@#### ', LEAST(GREATEST(I,1),27), 1)),'') FROM (
SELECT IX, IY, MAX(I) AS I FROM Z GROUP BY IY, IX ORDER BY IY, IX ) AS ZT
GROUP BY IY ORDER BY IY;