From 84adefa331c4159d432d22840663c38f155cd4c1 Mon Sep 17 00:00:00 2001
From: Erlang/OTP <otp@erlang.org>
Date: Fri, 20 Nov 2009 14:54:40 +0000
Subject: The R13B03 release.

---
 lib/gs/examples/frac.erl | 154 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 154 insertions(+)
 create mode 100644 lib/gs/examples/frac.erl

(limited to 'lib/gs/examples/frac.erl')

diff --git a/lib/gs/examples/frac.erl b/lib/gs/examples/frac.erl
new file mode 100644
index 0000000000..139a4be310
--- /dev/null
+++ b/lib/gs/examples/frac.erl
@@ -0,0 +1,154 @@
+%%
+%% %CopyrightBegin%
+%% 
+%% Copyright Ericsson AB 1996-2009. All Rights Reserved.
+%% 
+%% The contents of this file are subject to the Erlang Public License,
+%% Version 1.1, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Erlang Public License along with this software. If not, it can be
+%% retrieved online at http://www.erlang.org/.
+%% 
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%% 
+%% %CopyrightEnd%
+%%
+
+%%
+%% Purpose : Fractal trees
+
+-module(frac).
+
+-export([start/0, go/0, test/0, grow/2, expand/3, subst/2]).
+
+%% 0L - grammer -- context insensitive lindenmayer grammer
+
+start() ->
+    spawn(frac,go,[]).
+
+go() ->
+    draw(),
+    receive
+	_X -> true
+    end.
+
+draw() ->
+    S=gs:start(),
+    Width = 800,
+    Ht = 520,
+    Title="Context Insensitive Lindenmayer Grammer (L0) Trees",
+    Win=gs:create(window,S,[{title,Title},{width,Width},{height,Ht}]),
+    Canvas=gs:create(canvas,Win,[{width,Width},{height,Ht},{bg,{237,224,189}}]),
+    gs:config(Win,[{iconname,"Plants"},{map,true}]),
+    draw(Canvas, 1, Width, Ht),
+    draw(Canvas, 2, Width, Ht),
+    draw(Canvas, 3, Width, Ht),
+    draw(Canvas, 4, Width, Ht).
+
+draw(Graph, Index, Width, Ht) ->
+    draw_frac(Graph, Index, Width, Ht).
+    
+test() ->
+    grow(3,1).
+
+grow(NGens, RuleNumber) ->
+    lists:flatten(expand(NGens, RuleNumber, [a])).
+
+rule(1,a) -> [b,'[',a,']',b,'(',a,')',a];
+rule(1,b) -> [b,b];
+
+rule(2,a) -> [b,'[',a,'[',b,a,']',']'];
+rule(2,b) -> [b,'(','(',b,')',a,')',c];
+rule(2,c) -> [c,d];
+
+rule(3,a) -> [d,'[',d,b,e,']','(',d,c,e,')'];
+rule(3,b) -> [d,'[',d,a,f,']','(',d,c,f,')',f];
+rule(3,c) -> [d,'[',d,b,g,']','(',d,a,g,')',g];
+
+rule(4,a) -> [c,'(',b,a,'(',b,')',')',c,'[',b,a,'[',b,']',']'];
+rule(4,b) -> [c,'(',b,e,')',c,'[',b,f,']'];
+rule(4,c) -> [g,c,c];
+
+rule(_,X) -> X.
+
+
+step(a) -> 1.0;
+step(b) -> 0.8;
+step(c) -> 0.6;
+step(d) -> 0.7;
+step(e) -> 0.6;
+step(f) -> 0.65;
+step(g) -> 0.75;
+step(_) -> 1.0.
+
+start_coords(1) -> {0.8,0.8};
+start_coords(2) -> {0.6,0.8};
+start_coords(3) -> {0.4,0.8};
+start_coords(4) -> {0.2,0.8};
+start_coords(_) -> {0.5, 0.5}.
+
+gens(1) -> 5;
+gens(_) -> 5.
+
+scale(1) -> 5;
+scale(2) -> 40;
+scale(3) -> 40;
+scale(4) -> 4;
+scale(_) -> 5.
+
+expand(0,_,X) ->
+    X;
+expand(N,Index,X) ->
+    expand(N - 1, Index, lists:flatten(subst(X, Index))).
+
+
+subst([],_) -> [];
+subst([H|T],Index) ->
+    [rule(Index,H)|subst(T,Index)].
+
+
+draw_frac(Id, Index, Width, Ht) ->
+    X0 = 100,
+    Y0 = 100,
+    {XScale,YScale} = start_coords(Index),
+    Xstart = trunc(X0 + Width*XScale),
+    Ystart = trunc(Y0 + Ht*YScale),
+    Angle = 270.0 * 3.14159 / 180.0,
+    Scale = scale(Index),
+    N = gens(Index),
+    Tree = grow(N,Index),
+    drawit(Tree, Id, Xstart, Ystart, Angle, Scale, []).
+
+% drawit(Tree,S0,S).
+
+drawit([],_,_,_,_,_,_) ->
+    true;
+drawit(['('|T],Id,X0,Y0,Ang,Scale,Stack) ->
+    Ang1 =  Ang + (20.0 * 3.14159 / 180.0),
+    Scale1 = Scale * 0.8,
+    drawit(T,Id,X0,Y0,Ang1,Scale1,[{X0,Y0,Ang,Scale}|Stack]);
+drawit(['['|T],Id,X0,Y0,Ang,Scale,Stack) ->
+    Ang1 = Ang - (40.0 * 3.14159 / 180.0),
+    Scale1 = Scale * 0.8,
+    drawit(T,Id,X0,Y0,Ang1,Scale1,[{X0,Y0,Ang,Scale}|Stack]);
+drawit([')'|T],Id,_,_,_,_,[{X1,Y1,Ang1,Scale1}|Stack]) ->
+    drawit(T,Id,X1,Y1,Ang1,Scale1,Stack);
+drawit([']'|T],Id,_,_,_,_,[{X1,Y1,Ang1,Scale1}|Stack]) ->
+    drawit(T,Id,X1,Y1,Ang1,Scale1,Stack);
+drawit([Symbol|T],Id,X0,Y0,Ang,Scale,Stack) ->
+    Size = step(Symbol),
+    L = Size * Scale,
+    {X1, Y1} = plotit(Id,X0,Y0,L,Ang),
+    drawit(T,Id,X1,Y1,Ang,Scale,Stack).
+
+plotit(Id,X0,Y0,L,A) ->
+    CosA = math:cos(A),
+    SinA = math:sin(A),
+    X = trunc(X0 + L*CosA),
+    Y = trunc(Y0 + L*SinA),
+    gs:create(line,Id,[{coords,[{X0,Y0},{X,Y}]}]),
+    {X,Y}.
+	
-- 
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