[svn:parrot] r9521 - in trunk: . examples/pir t/examples

[bernhard]

Author: bernhard
Date: Thu Oct 20 13:14:04 2005
New Revision: 9521

Added:
   trunk/examples/pir/circle.pir
Modified:
   trunk/MANIFEST
   trunk/t/examples/pir.t
Log:
Added a circle drawing example in PIR.
Thanks to Nick Glencross  [perl #37487]

Added a test for circle.pir.


Modified: trunk/MANIFEST
==============================================================================
--- trunk/MANIFEST      (original)
+++ trunk/MANIFEST      Thu Oct 20 13:14:04 2005
@@ -599,6 +599,7 @@ examples/pasm/99beer.pasm               
 examples/pasm/cat.pasm                            [main]doc
 examples/pasm/fact.pasm                           [main]doc
 examples/pasm/hello.pasm                          [main]doc
+examples/pir/circle.pir                           [main]doc
 examples/pir/euclid.pir                           [main]doc
 examples/pir/hanoi.pir                            [main]doc
 examples/pir/mandel.pir                           [main]doc

Added: trunk/examples/pir/circle.pir
==============================================================================
--- (empty file)
+++ trunk/examples/pir/circle.pir       Thu Oct 20 13:14:04 2005
@@ -0,0 +1,119 @@
+# Copyright (C) 2005 The Perl Foundation.  All rights reserved.
+# $Id$
+
+=head1 NAME
+
+examples/pir/circle.pir - Draw a circle on any VT100-compatible screen
+
+=head1 SYNOPSIS
+
+    % ./parrot examples/pir/circle.pir
+
+=head1 DESCRIPTION
+
+This draws an ASCII-art representation of a circle (or oval) using only
+integer arithmetic and no trig.
+
+The algorithm is based on:
+
+  cos(theta+delta) =
+            cos(theta) -
+            [alpha*cos(theta) + beta*sin(theta)]
+
+and
+
+  sin(theta+delta) =
+            sin(theta) -
+            [alpha*sin(theta) - beta*cos(theta)]
+
+where
+
+  alpha = 2*sin^2(delta/2) and beta = sin(delta)
+
+(See Numerical Recipes in C / The Art of Scientific Computing)
+
+In this program the value of delta is chosen to be 1/(1<<n) such
+that it is small enough that
+
+=over 4
+
+=item * alpha is approximately 0
+
+=item * beta is approximately delta
+
+=back
+
+=head1 AUTHOR
+
+Written for parrot by Nick Glencross <[EMAIL PROTECTED]>. Adapted
+from a machine code program that I wrote for a BBC micro.
+
+=head1 COPYRIGHT
+
+Same as parrot.
+
+=cut
+
+.sub circle :main
+
+    # These are configurable depending on your screen size
+    .local int width, height
+    width  = 80
+    height = 24
+
+    # Calculate screen scaling and offset constants
+    .local int offset_x, offset_y, scale_x, scale_y
+    offset_x = width  / 2
+    offset_y = height / 2
+
+    scale_x  = 140000 / width
+    scale_y  = 140000 / height
+
+     # Clear the screen
+    print  "\033[H\033[2J"
+
+     # Initialise values
+    .local int x, y, counter
+    x = 0
+    y = 65536
+    counter = 0
+
+LOOP:
+
+    # Calculate screen coordinates
+    .local int screen_x, screen_y
+    screen_x  = x / scale_x
+    screen_x += offset_x
+
+    screen_y  = y / scale_y
+    screen_y += offset_y
+
+    print  "\033["
+    print  screen_y
+    print  ";"
+    print  screen_x
+    print  "H*"
+
+    # The magic to compute the next position
+    .local int temp1, temp2
+    temp1 = x >> 6
+    temp2 = y >> 6
+    x += temp2
+    y -= temp1
+
+    # Loop again
+    inc counter
+    if counter < 404 goto LOOP
+
+    # Place cursor back at bottom of screen
+    print  "\033["
+    print  height
+    print  ";0H"
+    print "\n"
+
+    # Done!
+    end
+
+.end
+
+# vim: ft=imc sw=4:

Modified: trunk/t/examples/pir.t
==============================================================================
--- trunk/t/examples/pir.t      (original)
+++ trunk/t/examples/pir.t      Thu Oct 20 13:14:04 2005
@@ -32,7 +32,7 @@ Bernhard Schmalhofer - <Bernhard.Schmalh
 =cut
 
 use strict;
-use Parrot::Test tests => 4;
+use Parrot::Test tests => 5;
 use Test::More;
 use Parrot::Config;
 
@@ -40,6 +40,9 @@ my $PARROT = ".$PConfig{slash}$PConfig{t
 
 # Set up expected output for examples
 my %expected = (
+    'circle.pir'        =>  << 'END_EXPECTED',
+********************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************
+END_EXPECTED
     'euclid.pir'        =>  << 'END_EXPECTED',
 Algorithm E (Euclid's algorithm)
 The greatest common denominator of 96 and 64 is 32.