2020-11-26 19:47:57 +00:00
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NEW
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AUTO 3,1
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2020-11-29 13:16:39 +00:00
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#!/bin/forth
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2020-11-26 19:47:57 +00:00
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\ Setup constants to remove magic numbers to allow
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\ for greater zoom with different scale factors.
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2020-11-29 13:16:39 +00:00
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20 CONSTANT MAXITER
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2020-11-26 19:47:57 +00:00
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-39 CONSTANT MINVAL
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2020-11-29 13:16:39 +00:00
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40 CONSTANT MAXVAL
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20 32 * CONSTANT RESCALE
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2020-11-26 19:47:57 +00:00
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RESCALE 4 * CONSTANT S_ESCAPE
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\ These variables hold values during the escape calculation.
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0 VARIABLE CREAL
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0 VARIABLE CIMAG
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0 VARIABLE ZREAL
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0 VARIABLE ZIMAG
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0 VARIABLE COUNT
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\ Compute squares, but rescale to remove extra scaling factor.
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: ZR_SQ ZREAL @ DUP RESCALE */ ;
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: ZI_SQ ZIMAG @ DUP RESCALE */ ;
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\ Translate escape count to ascii greyscale.
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: .CHAR
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S" ..,'~!^:;[/<&?oxOX# "
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DROP + 1
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TYPE ;
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\ Numbers above 4 will always escape, so compare to a scaled value.
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: ESCAPES?
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S_ESCAPE > ;
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\ Increment count and compare to max iterations.
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: COUNT_AND_TEST?
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COUNT @ 1+ DUP COUNT !
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MAXITER > ;
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\ stores the row column values from the stack for the escape calculation.
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: INIT_VARS
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2020-11-29 13:16:39 +00:00
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32 * DUP CREAL ! ZREAL !
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32 * DUP CIMAG ! ZIMAG !
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2020-11-26 19:47:57 +00:00
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1 COUNT ! ;
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\ Performs a single iteration of the escape calculation.
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: DOESCAPE
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ZR_SQ ZI_SQ 2DUP +
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ESCAPES? IF
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2DROP
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TRUE
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ELSE
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- CREAL @ + \ leave result on stack
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2020-11-29 13:16:39 +00:00
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ZREAL @ ZIMAG @ RESCALE */ 2 *
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2020-11-26 19:47:57 +00:00
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CIMAG @ + ZIMAG !
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ZREAL ! \ Store stack item into ZREAL
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COUNT_AND_TEST?
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ENDIF ;
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\ Iterates on a single cell to compute its escape factor.
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: DOCELL
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INIT_VARS
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BEGIN
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DOESCAPE
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UNTIL
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COUNT @
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.CHAR ;
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\ For each cell in a row.
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: DOROW
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MAXVAL MINVAL DO
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DUP I
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DOCELL
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LOOP
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DROP ;
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\ For each row in the set.
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: MANDELBROT
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CR
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MAXVAL MINVAL DO
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I DOROW CR
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LOOP ;
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\ Run the computation.
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MANDELBROT
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MAN
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TEXT root/mandelbrot.f
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