==[]-- Embedding virtual slide rule in your page

If you have slide rule related web page and would like to give the user the ability to "try" slide rules you are writing about or to evaluate slide rule calculation examples, then you may wish to embed an emulator in your page.

This page describes how to do this with yet another slide rule emulator used throughout this site.

Internal information

The emulator is written in javascript with use of Internet Explorer browser and Netscape Navigator object model. This means that your page will not provide "virtual slide rule" for users without IE4.0 (or later) or NN4.04 (or later). (I did not have chance to test it on platforms other than Windows). However this should not provide any uncomfortable side effects and your page should still be viewable by other browsers (if it was designed to).

I do have plans to make emulator compatible with any Java capable browser but currently only IE and NN are supported.

Emulator consists of 3 parts:

  1. File createrule.js that contains interface functions to create virtual slide rule.
  2. File rule.htm that contains generic layout of the slide rule window and procedures for mouse and keyboard control.
  3. Set of picture files each of which represents single scale in appropriate resolution. The filename without extension and path is considered "scale ID" and used to identify the scale in slide rule layout description. Scale ID is case sensitive.
You do not need to have these files on your site in order to run emulator from your page.

Emulator location

Currently emulator is located on the NBCi.com web site that provides free web hosting. It is located in the folder http://members.nbci.com/_XMCM/nsg21/slide/yasre. Wherever later in this page you are asked to enter "emulator location" you should enter this folder.

For some reasons NBCi site may become unavailable from time to time and emulator will not be available to visitors of your page at those moments. You may download the whole emulator (.zip is available) to you own site and use it locally. In this case you should use the url of the folder you put it in wherever "emulator location" is mentioned. Please, drop me e-mail if you choose to do it this way.

The drawback of this approach is that your page will not use the latest and best version of the emulator. Drop me e-mail if you want me to send you notification when new version is ready. I do not do this often, so, do not be afraid that I will overwhelm your mailbox.

Changes to your page

First of all you will need to add line 
<script	src="emulator_location/createrule.js"></script>
in the very beginning of your file (for example in <HEAD> section). This may be 
<script	src="http://members.nbci.com/_XMCM/nsg21/slide/yasre/createrule.js"></script>
if you are using original location, or 
<script	src="./yasre/createrule.js"></script>
if you are using local copy.

This script file contains function create_rule(rt,rd[,rn]) that (when called with appropriate parameters) will create new window with a slide rule. The parameters are:

rt
String containing location of slide rule template file -- rule.htm. Consists of emulator location folder and file name. For example: "http://members.nbci.com/_XMCM/nsg21/slide/yasre/rule.htm"
rd
String with slide rule scale layout. Contains comma separated list of scales present on your rule in the order from top to bottom with slide scales emphasised with '[' and ']'. For duplex rules back side may be entered separated by the front side with '/'. For example: "A[B,C]D/DF[CF,C]D". Scale IDs are case sensitive. According to convention, scales whose IDs ending with '~' always point downwards, scales ending with '_' always point upwards. The list of available scales can be obtained from scale selector form. The scale list is by no means full, but I am working on this. Please drop me e-mail with the scale you want to be added, its formula, ID and slide rule where it is used.
rn
String with rule name. For example "Pickett N4-ES". Will just appear in the window title.
It is a nice idea to define a variable with rule template location 
<script><!--
var RULETEMP="http://members.nbci.com/_XMCM/nsg21/slide/yasre/rule.htm";
//--></script>
somewhere in your code (preferrably in the <HEAD> section), if you are going to use it more than once.

Button

With this definition you may create button control that will create virtual slide rule when pressed. For example: 
<form><input
 value="Create slide rule"
 type=button
 onclick="create_rule(RULETEMP,'A[B,C]D','Mannheim')"
></form>

Hyperlynk

Another approach is to use hyperlink. The html code example: 

<p>This	calcualation can be easily performed with
<a href=javascript:create_rule(RULETEMP,'S~,A[B,S~,-,T,C]D,T','Unique')>
Unique navigational</a> slide rule.

Hyperlynk in harsh environment

Virtual slide rule hyperlinks on these pages follow another approach. The reason for this is that pages can be viewed either directly or in a frame of NBCi envelope. In latter case the method described above will not work for some reasons (still mysterious for me). If your page also have chances to be displayed as a frame in aggresive parent frameset (for example, it may try to manipulate its children's hyperlinks like NBCi envelope does), you may try the following method: 
<a href=javascript:noaction() onclick=javascript:create_rule(RULETEMP,"R1[R1~,R2_]R2",'Precision')>
Try</a> to multiply using extended precision	scales.

Here fake href provides distinguished formatting that allows visually identify entity as a hyperlink, "hand" cursor when hovered over and tab stop when navigating using keyboard. Actual job is done by onclick clause. Function noaction() is defined in file createrule.js and does nothing. Its only purpose is to provide syntactically correct link.

This site also uses stylesheet to color this kind of hyperlinks in green color -- to distingush them from regular ones.

Copyright and license

"Yet another slide rule emulator" is copyright (C) 2000 by Andrew Nikitin. This software is provided ``as is'' and without any express or implied warranties, including, without limitation, the implied warranties of merchantability and fitness for a particular purpose. You may use it free of charge. "Do not eat".
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The contents of this page have not been reviewed or approved by the University of Minnesota.