jgamble’s gists

jgamble / hercbyte.asm

Created January 27, 2023 04:34

Like hercdot.asm, write pixels onto the screen with the Hercules graphics card, but a byte's worth at a time instead of pixel by pixel., which was a significant speed-up on 8086 computers.

	;
	; Hercbyt -- write out a byte's worth of dots in the correct position
	; for the Hercules graphics board. This is a variation on hercdot,
	; which writes out only a dot at a time.
	;
	; Invocation: hercbyt(the_byte, y, x)
	; the_byte = {0..255}
	; y = {0..347}
	; x = {0..712}, a multiple of 8, to stay on a byte boundry.
	;

jgamble / hercdot.asm

Created January 27, 2023 04:02

Very old code from 1985. Set a pixel on the screen using the Hercules graphics card (see https://en.wikipedia.org/wiki/Hercules_Graphics_Card).

	;
	; Hercdot -- write out a dot in the correct position for the Hercules
	; graphics board. There are only two colors available: black or white.
	;
	; Invocation: hercdot(color, y, x)
	; color = {0, 1}
	; y = {0..347}
	; x = {0..719}
	;
	; In order to use the hercules graphics board, you have to

jgamble / hercmode.asm

Created January 27, 2023 03:39

Very old code from 1987. Switch the Hercules Graphics Card (see https://en.wikipedia.org/wiki/Hercules_Graphics_Card) to graphics mode or text mode.

	; HERCMODE -- Mode switch for Hercules Graphics board.
	; Copied from the Hercules owner's manual, edition 2.1, pg 20.
	;
	; port address
	index equ 03b4h
	cntrl equ 03b8h
	;
	; control codes
	scrn_on equ 8
	grph equ 2

jgamble / PrimeOffsetArray.c

Created October 16, 2019 21:33

Simply a pair of arrays to create the highest (or lowest) prime that is n bits wide. Entered as C, but written in an array form that should be common across most languages. See comments below.

	//
	// Offsets for creating the highest prime that fits in n bits; the
	// highest prime less than 2**n.
	//
	// n can range from 1 .. 128. If arrays are zero-based in the language
	// you want to use, subtract 1 from n before indexing.
	//
	// I.e.,
	// hp24 = (1 << 24) - hiprimeoffset[24];
	//

jgamble / imp_triangle.ps

Created June 19, 2018 21:03

Impossible Triangle Illusion in Postscript, by Guy Shaw (circa 1990)

	%!
	% M. C. Escher style impossible triangle
	% written by Guy Shaw

	% Things that are easy to play with:
	% Position on paper, overall size, and linewidth
	/inch { 72 mul } bind def

	2 inch dup translate
	3 inch dup scale

jgamble / hexpaper.ps

Last active June 19, 2018 19:55

Hexpaper In Postscript, by Daniel C. Nygren (posted on USENET in 1994). Settings (hex size, page size, etc) are set in-place, I've never felt the need to write a wrapper for it.

	%!PS-Adobe-1.0
	% hexpaper.ps - Version 1.0 : Hexagon mapping paper in PostScript
	%
	% Copyright 1994 by Daniel C. Nygren
	% Current e-mail: nygren@tecnet1.jcte.jcs.mil
	%
	% Permission to use and modify this software for any purpose other than
	% commercial use or its incorporation into a commercial product is
	% hereby granted without fee. Permission to copy and distribute this software
	% only for non-commercial use is also granted without fee, provided that

jgamble / bitpattern.pl

Created April 17, 2018 01:37

Create a list of bits according to the cyclic pattern you provide. The list may then be used as-is, joined to form a string, or packed into an integer.

	#
	# @bits = bitpattern($pattern, $length, $offset);
	#
	# Create a list of bits in a cyclic pattern.
	#
	# $pattern is an array reference containing the on (ones) and
	# off (zeros) sequence of the pattern.
	#
	# $length is the length of the bitpattern to return.
	#

jgamble / hexdist.pl

Last active June 27, 2016 04:15

Find the distance between two points on a hexagonal grid. Problem defined by Pete Stewart in 2002, solved by Tom Ruschak and Tanya Gilham.

	#
	# For calculating the diagonal distance, it is important to
	# know which columns are shifted up (see the diagram below in
	# the hexagon_distance() function).
	#
	# For the purposes of this code snippet we have a simple
	# function that defines the odd-numbered columns as 'up'.
	#
	sub upcolumn
	{

jgamble / spiro.f

Last active October 23, 2018 22:44

Spirograph simulation -- rediscovered the code from an August 1983 printout. There are two routines, SPIRO and XPIRO

	C
	C Subroutine spiro simulates the designs of the toy spirograph.
	C Where:
	C R1 -- The radius of the stationary wheel.
	C R2 -- The radius of the moving 'pen' wheel.
	C P -- The pen's distance from the center of the 'pen' wheel.
	C ANGLE -- The angle by which the drawn figure is rotated, in degrees.
	C STEP -- The increment of rotation of the pen wheel around the
	C stationary wheel, in degrees.
	C X, Y -- Arrays to hold the X and Y coordinates of the design.

jgamble / list_from_file.pl

Created April 20, 2016 22:35

Perl function for quick read of a list file

	=head3 list_from_file()

	@list = &list_from_file($filename, $comment_patrn, $keep_empty);

	$filename - The file to open.
	$comment_patrn - (Optional) A pattern that represents end-of-line style comments.
	$keep_empty - (Optional) Add or do not add empty (no non-blank characters) lines.

	Take a file containing a list of items. For each line, strip off any
	characters following and including the comment character(s). Strip off

John M. Gamble jgamble