18 lines
612 B
MySQL
18 lines
612 B
MySQL
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WITH RECURSIVE
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xaxis(x) AS (VALUES(-2.0) UNION ALL SELECT x+0.05 FROM xaxis WHERE x<1.2),
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yaxis(y) AS (VALUES(-1.0) UNION ALL SELECT y+0.1 FROM yaxis WHERE y<1.0),
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m(iter, cx, cy, x, y) AS (
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SELECT 0, x, y, 0.0, 0.0 FROM xaxis, yaxis
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UNION ALL
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SELECT iter+1, cx, cy, x*x-y*y + cx, 2.0*x*y + cy FROM m
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WHERE (x*x + y*y) < 4.0 AND iter<28
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),
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m2(iter, cx, cy) AS (
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SELECT max(iter), cx, cy FROM m GROUP BY cx, cy
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),
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a(t) AS (
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SELECT group_concat( substr(' .+*#', 1+min(iter/7,4), 1), '')
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FROM m2 GROUP BY cy
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)
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SELECT group_concat(rtrim(t),x'0a') as Mandelbrot FROM a;
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