added 13-bounce for Perl

13_Bounce/perl/README.md

@@ -1,3 +1,6 @@
 Original source downloaded [from Vintage Basic](http://www.vintage-basic.net/games.html)
 
 Conversion to [Perl](https://www.perl.org/)
+
+Added feature so that if "TIME" value is "0" then it will quit,
+so you don't have to hit Control-C. Also added a little error checking of the input.

13_Bounce/perl/bounce.pl

@@ -0,0 +1,91 @@
+#!/usr/bin/perl
+
+# Bounce program in Perl
+# Translated by Kevin Brannen (kbrannen)
+
+use strict;
+use warnings;
+
+print "\n";
+print " " x 31,"BOUNCE\n";
+print " " x 15, "CREATIVE COMPUTING  MORRISTOWN, NEW JERSEY\n";
+print "\n\n\n";
+
+print "THIS SIMULATION LETS YOU SPECIFY THE INITIAL VELOCITY\n";
+print "OF A BALL THROWN STRAIGHT UP, AND THE COEFFICIENT OF\n";
+print "ELASTICITY OF THE BALL.  PLEASE USE A DECIMAL FRACTION\n";
+print "COEFFICIENCY (LESS THAN 1).\n\n";
+print "YOU ALSO SPECIFY THE TIME INCREMENT TO BE USED IN\n";
+print "'STROBING' THE BALL'S FLIGHT (TRY .1 INITIALLY).\n\n";
+
+# deal with basic's tab() for line positioning
+#   line = line string we're starting with
+#   pos = position to start writing
+#   s = string to write
+# returns the resultant string, which might not have been changed
+sub line_tab
+{
+    my ($line, $pos, $s) = @_;
+    my $len = length($line);
+    # if curser is past position, do nothing
+    if ($len <= $pos) { $line .= " " x ($pos - $len) . $s; }
+    return $line;
+}
+
+while (1)
+{
+    my @T;          # time slice?
+    my $time_inc;   # time increment, probably in fractions of seconds
+    my $velocity;   # velocity in feet/sec
+    my $coeff_elas; # coeeficent of elasticity
+    my $L;          # position on line
+
+    # get input
+    print "TIME INCREMENT (SEC, 0=QUIT): "; chomp($time_inc = <>);
+    last if ($time_inc == 0);
+    print "VELOCITY (FPS): "; chomp($velocity = <>);
+    print "COEFFICIENT: "; chomp($coeff_elas = <>);
+    if ($coeff_elas >= 1.0 || $coeff_elas <= 0)
+    {
+        print "COEFFICIENT MUST BE > 0 AND < 1.0\n\n\n";
+        next;
+    }
+
+    print "\nFEET\n";
+    my $S1 = int(70.0 / ($velocity / (16.0 * $time_inc)));
+    for my $i (1 .. $S1)
+    {
+        $T[$i] = $velocity * $coeff_elas ** ($i - 1) / 16.0;
+    }
+
+    # draw graph
+    for (my $height=int(-16.0 * ($velocity / 32.0) ** 2.0 + $velocity ** 2.0 / 32.0 + .5) ; $height >= 0 ; $height -= .5)
+    {
+        #print "h=$height\n"; # kevin
+        if (int($height) == $height) { print sprintf("%2d", $height); }
+        else                         { print "  "; }
+        $L = 0;
+        my $curr_line = "";
+        for my $i (1 .. $S1)
+        {
+            my $time;
+            for ($time=0 ; $time <= $T[$i] ; $time += $time_inc)
+            {
+                $L += $time_inc;
+                next if (abs($height - (.5 * (-32) * $time ** 2.0 + $velocity * $coeff_elas ** ($i - 1) * $time)) > .25);
+                $curr_line = line_tab($curr_line, ($L / $time_inc), "0");
+            }
+            $time = ($T[$i + 1] // 0) / 2;
+            last if (-16.0 * $time ** 2.0 + $velocity * $coeff_elas ** ($i - 1) * $time < $height);
+        }
+        print "$curr_line\n";
+    }
+
+    print "  .";
+    print "." x (int($L + 1) / $time_inc + 1), "\n";
+    print "  0";
+    my $cl = "";
+    for my $i (1 .. int($L + .9995)) { $cl = line_tab($cl, int($i / $time_inc), $i); }
+    print "$cl\n";
+    print " " x (int($L + 1) / (2 * $time_inc) - 2), "SECONDS\n\n";
+}