Fixing up example.

[forth.jl.git] / examples / mandelbrot.4th

diff --git a/examples/mandelbrot.4th b/examples/mandelbrot.4th
index 2767738..5707acb 100644 (file)
--- a/examples/mandelbrot.4th
+++ b/examples/mandelbrot.4th
@@ -1,42 +1,85 @@
-( --- Complex integer arithmetic --- )
+( --- Complex arithmetic --- )
+
+( Location of floating point. )
+: precision 10000 ;
+
+: sign dup abs / ;
+
+: >scaled
+    precision 10 / * over
+    ?dup 0<> if 
+        sign *
+    then
+    swap precision * +
+;
+
+( Redefine multiplication.  Yay forth! )
+: * precision */ ;
 
 : c* ( x1 y1 x2 y2 -- x3 y3 )
-        swap rot                ( x1 x2 y1 y2 )
-        2dup * negate           ( x1 x2 y1 y2 -y1y2 )
-        4 pick 4 pick * +       ( x1 x2 y1 y2 (x1x2-y1y2))
-        4 roll 2 roll *         ( x2 y1 (x1x2-y1y2) x1y2 )
-        3 roll 3 roll * +       ( (x1x2-y1y2) (x1y2+x2y1) )
+    swap -rot               ( x1 x2 y1 y2 )
+    2dup * negate           ( x1 x2 y1 y2 -y1y2 )
+    4 pick 4 pick * +       ( x1 x2 y1 y2 (x1x2-y1y2))
+    4 roll 2 roll *         ( x2 y1 (x1x2-y1y2) x1y2 )
+    3 roll 3 roll * +       ( (x1x2-y1y2) (x1y2+x2y1) )
 ;
 
 : c+ ( x1 y1 x2 y2 -- x3 y3 )
-        rot +
-        -rot +
-        swap
+    rot +
+    -rot +
+    swap
 ;
 
 : csq 2dup c* ;
 
-; cmagsq ( x1 y1 -- mag )
-        csq abs
+: cmagsq ( x1 y1 -- mag )
+    csq abs
 ;
 
 ( --- Mandelbrot set calculations  --- )
 
 : iterate ( cr ci zr zi -- cr ci z'r z'i )
-        csq c+
+    csq c+
 ;
 
 : inSet? ( cr ci -- res )
+    DEBUGON
+
+    0 0     ( z_0 = 0 )
     
-    100 0 DO
+    true    ( flag indicating set membership )
+    100 0 do
+        drop
 
-        2SWAP 2DUP 5 ROLL 5 ROLL
         iterate
-        2DUP cmagsq
-        100 > IF
-            LEAVE
-        THEN
+        2dup cmagsq
+        4 >scaled > if
+            false ( not in set )
+            leave
+        then
+
+        true ( maybe in set )
+    loop
+
+    ( Clear z and c, leaving set membership flag ) 
+    -rot 2drop -rot 2drop
+;
+
+: xsteps 100 ;
+: ysteps 50 ;
+
+( Draw the Mandelbrot Set!)
+: mandel ( x1 y1 x2 y2 -- )
 
-    LOOP
+    1 pick 4 pick -
+    2 pick 5 pick do
+        i 0 inSet? if
+            42 emit
+        else
+            '.' emit
+        then
+    dup +loop
 ;
 
+( Clean up - hide non-standard multiplication def. )
+hide *