41 lines
1.2 KiB
Common Lisp
41 lines
1.2 KiB
Common Lisp
[set-graphics 1]
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; Constants.
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[let WIDTH 320]
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[let HEIGHT 200]
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[let MAXIT 15]
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[let FIXED 500]
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; Fixed-point arithmetic.
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[let mf [fun [x] [* x FIXED]]]
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[let *f [fun [x y] [muldiv x y FIXED]]]
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; Complex numbers.
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[let re [fun [z] [car z]]]
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[let im [fun [z] [cdr z]]]
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[let +c [fun [a b] [cons [+ [re a] [re b]] [+ [im a] [im b]]]]]
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[let square-c [fun [z] [cons
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[- [*f [re z] [re z]] [*f [im z] [im z]]]
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[* 2 [*f [re z] [im z]]]]]]
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[let length-squared [fun [z] [+ [*f [re z] [re z]] [*f [im z] [im z]]]]]
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; Viewport.
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[let getx [fun [x] [- [muldiv x [mf 3] WIDTH] [mf 2]]]]
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[let gety [fun [y] [- [muldiv y [mf 2] HEIGHT] [mf 1]]]]
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; Image generation.
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[let iterate [fun [z c] [+c c [square-c z]]]]
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[let do_pixel [fun [X Y c] [let i 0] [let z c]
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[while [and [< i MAXIT] [<= [length-squared z] [mf 4]]]
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[do [= z [iterate z c]] [inc i]]]
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[poke 10 [+ X [* 320 Y]] [+ 64 i]]]]
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[let do_row [fun [Y y] [let col 0] [while [< col WIDTH]
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[do [do_pixel col Y [cons [getx col] y]] [inc col]]]]]
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[let image [fun [] [let row 0] [while [< row HEIGHT]
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[do [do_row row [gety row]] [inc row]]]]]
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; Show the image and wait for user input.
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[image]
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[wait-key]
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[set-graphics nil]
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