wallet/docs/writing_and_editing_documentation.md

title: >- Writing and Editing Documentation # katex

Pandoc Markdown

Much documentation is in Pandoc markdown, because easier to write. But html is easier to read, and allows superior control of appearance

To convert Pandoc markdown to its final html form, invoke Pandoc by the bash shell file ./mkdoc.sh, which generates html.

In the windows 10 environment, shell scripts used in this project need to be associated with Git Bash or run from within Git Bash.

If the title in the markdown file is followed by # katex, as in the markdown form of this file, the shell script will tell Pandoc to display any formulae using katex in the html file.

More precisely, if any of the first three lines in the yaml header specifying the title at the start of the markdown file are # katex, the ./mkdoc.sh will tell Pandoc to use katex to display maths formula.

This vast pile of notes is out of control, and writing code and maths in html leads to intolerable overheads.

Hence markdown, the popular markdown conversion program being the open source Pandoc.

Markdown converters are apt to throw a flood of incomprehensible html code into your final document, taking low level html control away from the writer.

Pandoc, however, will allow you to take control. To integrate html and css with markdown using Pandoc is a bit like rolling marbles with your elbows through a cage. One has to work through and around the entry points that Pandoc gives you, while if you were writing in html you could just write what you damn well wanted directly, but having done the work, Pandoc can then ensure it is done for every document in the same style in the same way, and you can change the final form of every document in the same way all at once.

Sphinx is very popular and widely used, and written in the far more accessible language python, but to access the power of html, css, and JavaScript one must write a Sphinx theme, and the creation of a Sphinx theme is less than well documented and appears to be subject to change.

Visual Studio Code theoretically does automatic generation of the html equivalents of markdown files, but I never was able to get it working satisfactorily.

Pandoc has a number of powerful extensions that allow integration of html and markdown, among them markdown native mode divs :::

::: {style="…"}
	…
:::

And native mode spans […]{style="…"}

Which extensions do not work correctly in Visual Studio Code.

These can be used to put an anchor in text, but the easiest and most intelligible way to insert an anchor is as a header.

Pandoc can do a good job of rendering math markdown without invoking katex, and in such cases, one should generate the html

fn=filename
 pandoc --toc --eol=lf	--wrap=preserve --from markdown+ascii_identifiers --to html --metadata=lang:en --verbose --include-in-header=./pandoc_templates/header.pandoc --include-before-body=./pandoc_templates/before.pandoc --include-after-body=./pandoc_templates/after.Pandoc -o $fn.html $fn.md

Since markdown has no concept of a title, Pandoc expects to find the title in a yaml inline, which is most conveniently put at the top, which renders it somewhat legible as a title.

Thus the markdown version of this document starts with:

---
title: >-
	Writing and Editing Documentation
# katex
---

Converting html source to markdown source

In bash

fn=foobar
git mv $fn.html $fn.md && cp $fn.md $fn.html && pandoc -s --to markdown-smart --eol=lf --wrap=preserve --verbose -o $fn.md $fn.html

Math expressions and katex

Pandoc can render most maths markdown without needing katex, for example:

{e}^{i\pi}+1=0

a=b+c

f(x) = x^2

\sin(\pi/6) = 0.5

\int_a^b f(x) dx

\int_a^b \tan(x) dx

\int \sin(x) dx = \cos(x)

\sum a_i

\lfloor{(x+5)÷6}\rfloor = \lceil{(x÷6}\rceil

\lfloor{(x+5)/6}\rfloor = \lceil{(x/6}\rceil

Using Omicron, \bigcirc, not capital O for big \bigcirc. \Omicron will not always compile correctly, but \ln and \log is more likely to compile correctly than ln and log, which it tends to render as symbols multiplied, rather than one symbol.

\ln(1+x)=x-\bigcirc(x^2)

H(a|b|v)

though it is subtly prettier with katex, and some maths expressions will break Pandoc unless one tells it to use katex.

Some maths, Pandoc needs katex:

\sin(\frac{\pi}{6}) = \frac12

\displaystyle\frac{u(x)}{v(x)}

Inline equation \displaystyle\sum\limits_{i=1}^n i^2 = \frac{n(n+1)(2n+1)}{6} text after inline equation

\displaystyle\sum\limits_{i} i^2 = \frac{i(i+1)(2i+1)}6

The square root of 100 is \sqrt{100}=10.
The cubic root of 64 is \sqrt[3]{64}=4

\bigg\lfloor\frac{x+5)}{6}\bigg\rfloor = \bigg\lceil{\frac{x}{6}}\bigg\rceil

So for documents requiring some heavy maths display, we convert from markdown to html with, in the bash script ./mkdoc.sh:

fn=filename
pandoc --katex=./ --toc --eol=lf  --wrap=preserve --from markdown --to html --metadata=lang:en --verbose --include-in-header=./pandoc_templates/header.pandoc --include-before-body=./pandoc_templates/before.pandoc --include-after-body=./pandoc_templates/after.pandoc -o $fn.html $fn.md

The ./ tells pandoc to expect to find the files

./katex.min.css
./katex.min.js

That a file needs katex is flagged for ./mkdoc.sh in the yaml header.

A file that does not need katex has the header:

---
title: >-
	Document title
---

But if it does need katex, it has the header

---
title: >-
	Document title
 # katex
---

So that the bash script file ./mkdoc.sh will tell Pandoc to find the katex scripts.

For it offends me to put unnecessary fat in html files.

overly clever katex tricks

k \approx \frac{m\,l\!n(2)}{n}%uses\, to increase spacing, uses \! to merge letters, uses % for comments 

k \approx\frac{m\>\ln(2)}{n}%uses\> for a marginally larger increase in spacing and uses \ln, the escape for the well known function ln 

 \exp\bigg(\frac{a+bt}{x}\bigg)=\huge e^{\bigg(\frac{a+bt}{x}\bigg)}%use the escape for well known functions, use text size sets

k\text{, the number of hashes} \approx \frac{m\ln(2)}{n}% \text{} for render as text

\def\mydef#1{\frac{#1}{1+#1}} \mydef{\mydef{\mydef{\mydef{y}}}}%katex macro 

diagrams

The best way to do diagrams is svg and the Visual Studio Code scalable vector graphics extensions.

I decided to place the data directly inline in markdown because interfacing scalable vector graphics files (svg files) to html can get complicated, and interfacing the resulting complicated html to markdown can get more complicated.

Inkscape files are unreadable, and once they are cleaned up, Inkscape cannot read them. To (irreversibly) clean up an Inkscape file, minify it in Visual Studio Code to get rid of all confusing mystery cruft inserted by Inkscape, edit it back into markdown compatible form, and reinsert it in the markdown file.

A sequence of straight lines is M point, L point, L point.

Z and z draw a straight line back to the beginning, use in conjunction with fill="#red" , for example fill="#FF0000". If the line is open, fill="none"

H and h draw horizontal lines, V and v vertical lines. To see which line you are working on, convenient to temporarily begin and end it with a cross, h 3 h-6 h3 v3 v-6 v3

Drawing smooth curves by typing in text is painful and slow, but so is drawing them in Inkscape. Inkscape is apt to do a series of C beziers with sharp corners between them, and when I try to fix the sharp corners, the bezier goes weird.

If you can get your desired curve with a single M point c point point point that causes the least grief, and gives you a nice smooth curve.

The first point is the starting position, the last point is the end position. The direction of the first control point sets the starting direction, the direction of the second control point sets the end direction, and how far the control points are out controls how where the curve changes direction. If the curve is weird and pathological, there is something funny with your control points. Some control point positions lead to singularities in the derivative of the curv but for reasonable control point positions, you get a nice smooth curve.

Capital letters indicate absolute points, lower case relative points.

Before deciding you need to add additonal points to get the curve you want, see if you are doing something dumb with your control points. You usually are.

If you want a sharp turn coming out, and a smooth curve, then a sharp curve coming in to the destination, you do not put in a bunch of intermediate points, you just put your control points close to the beginning and end.

The further the control point is away from the end of the previous S curve, the further its influence propagates into the next S curve. Which can have surprising results if the next S curve is very short, so that influence of the previous control point propagates far beyond its end.

If you want a smooth and gentle curve, you want the last C or S control point to be around the middle of the curve, and its reflection in the next S curve to be around the middle of the next S curve

You only need additional points when you want the curve to go through a narrow pass, in which case you are going to have a C curve going to the narrow pass, and an S curve going to the destination or the next narrow pass.

When you want to join two points, and don't care about the path, use an L straight line

When you want to join two points, and you care about the direction in which it starts, or the direction in which it finishes, but not both, use a Q, which gives you one degree of control freedom.

When you want to join two points, and care about the direction it starts, and the direction it ends, use a C, which gives you two degrees of control freedom.

When you want to join two points, and care about the direction it starts, the direction it ends, and you want it to go through a gateway in the middle, use a C S, which gives you three degrees of control freedom. But watch out for the reflection of the last control point in the C landing somewhere difficult inside the S curve. If the last control point in the C is further from the end point of the C than the end point of the S, things can get strange. Sometimes you want to adjust the behavior of the S curve by moving the last control point of the previous C or S to the right position. A distant previous control point is apt to have a big effect on the following S, a near control point little effect, but likely to give you an unpleasantly sharp turn at the join.

M point c point point point s point point
s point point ... s point

Is guaranteed to give you a smooth curve, for reasonably sane control points, with the curve passing through the second point of the s, and its direction set by the first point of the s.

You change a control point, the effect is entirely local, does not propagate up and down the line.

M point q point point t point t point ... t point

Is also guaranteed to give you a nice smooth curve for any reasonably sane choice of the initial control point and the position of the t points, but you cannot easily control the direction the curve takes through the points. Changing the control point of the first q will result in things snaking all down the line, and changing any of the intermediate t points will change the the direction the curve takes through all subsequent t points, sometimes pushing the curve into pathological territory where bezier curves give unexpected and nasty results.

Scalable vector graphics are dimensionless, and the <svg> tag's height, width, and ViewBox properties translate the dimensionless quantities into pixels. The graphics default to fixed aspect ratio, and anything outside the viewbox is not drawn. To adjust your image's position within the viewbox, you put everything into a single big group, and apply a translate to that group.

The enormous advantage of scalable vector graphics is that it handles repetitious items in diagrams beautifully, because you can define an item by reference to another item, thus very large hierarchical structure can be defined by very small source code.

<svg
	xmlns="http://www.w3.org/2000/svg"
	width="29em"  height="12em"
	viewBox="40 60 60 50"
	style="background-color:ivory">
	<g  id="startblocks"
		font-family="'Times New Roman'" font-size="5"
		font-weight="400"
		stroke-width="2"
		style="text-decoration:underline; cursor:pointer;" >
		<line x1="22" y1="70" x2="28" y2="100" stroke="lightgrey"/>
		<rect style="fill:#FFFF00;"
			x="12" y="64" width="36" height="20">
			<animate attributeType="XML" attributeName="y"
				from="64" to="120"
				dur="5s" repeatCount="2" restart="always" />
		</rect>
		<text style="fill:blue;"  x="14" y="74">
			<animate attributeType="XML" attributeName="y"
				from="74" to="130"
				dur="5s" repeatCount="2" restart="always" />
			start animation
		</text>
	</g>
	<rect x="60" y="64" width="20" height="20">
		<animate attributeType="XML" attributeName="y"
			from="64" to="120"
			dur="5s" repeatCount="3" restart="whenNotActive"/>
	</rect>
	<g
		font-family="'Times New Roman'" font-size="5"
		font-weight="400"
		stroke-width="2">
		<path fill="none" stroke="#00f000"
			d="M14.629 101.381c25.856-20.072 50.69-56.814
			54.433-18.37 3.742 38.443 40.484 15.309 40.484 15.309"/>
		<ellipse cx="60" cy="85" rx="12" ry="5" style="fill:red" />
		<text  x="60" y="82" text-anchor="middle"  style="fill:#A050C0;" >
			A simple scalable vector graphic
			<tspan x="60" dy="8">
				directly embedded in markdown.
			</tspan>
		</text>
	</g>
</svg>

<script>
	document.getElementById("startblocks").addEventListener
	(
		"click", evt =>
		{
			document.querySelectorAll("animate").forEach
			(
				element =>
				{
					element.beginElement();
				}
			);
		}
	);
</script>

# tables

 <table border="1" cellpadding="6" cellspacing="0" width="95%">
      <tbody>
        <tr>
          <td colspan="2" style="background-color: #99CC66;
	text-align:center;">May Scale of monetary hardness </td>
        </tr>
        <tr>
          <td style="text-align:center;"><b> Hardness</b> </td>
          <td> <br/>
          </td>
        </tr>
        <tr>
          <td colspan="2" style=" text-align:center;">Hard</td>
        </tr>
        <tr>
          <td class="center"><b>1</b></td>
          <td>Street cash, US dollars</td>
        </tr>
        <tr>
            <td class="center"><b>2</b></td>
          <td>Street cash, euro currencies, japan</td>
        </tr>
        <tr>
          <td class="center"><b>3</b></td>
          <td>Major crypto currencies, such as Bitcoin and Monaro</td>
        </tr>
        <tr>
          <td class="center"><b>4</b></td>
          <td>Street cash, other regions</td>
        </tr>
        <tr>
          <td class="center"><b>5</b></td>
          <td>Interbank transfers of various sorts (wires etc),
              bank checks</td>
        </tr>
        <tr>
          <td class="center"><b>6</b></td>
          <td>personal checks</td>
        </tr>
        <tr>
          <td class="center"><b>7</b>
            </td>
          <td>Consumer-level electronic account transfers (eg
              bPay)</td>
        </tr>
        <tr>
          <td class="center"><b>8</b></td>
          <td>Business-account-level retail transfer systems</td>
        </tr>
        <tr>
          <td colspan="2" style=" text-align:center;">Soft</td>
        </tr>
        <tr>
          <td class="center"><b>9</b></td>
          <td>Paypal and similar 'new money' entities, beenz</td>
        </tr>
        <tr>
         <td class="center"><b>10</b></td>
          <td>Credit cards</td>
        </tr>
      </tbody>
    </table>

Tables

Pipe table with header and alignment control

Without counting spaces, but without multiline

Pipe table:

Right	Left	Default	Center
12	12	12	12
123	123	123	the quick brown fox jumped over the lazy dog
1	1	Carrian Corporation	1

And, with less mucking about, alignments

with alignment, without counting spaces, but without multiline

fruit	price
apple	2.05
pear	1.37
orange	3.09

multiline without bothering with pipes

Counting spaces to align. Only editable in fixed font

This allows multiline, but visual studio code does not like it. Visual Studio Code only supports tables that can be intelligibly laid out in visual studio code.

---

Centered Default Right Left Header Aligned Aligned Aligned

---

First row 12.0 Example of a row that spans multiple lines.

Second row 5.0 Here's another one. Note the blank line between rows.

The header may be omitted in multiline tables as well as simple tables

Notice the alignment is controlled by the first item in a column

In this table, edited in a fixed font, you are using whitespace and blank lines to lay out the table. It is unintellible in a variable width font.

---

First row 12.0 Example of a row that spans multiple lines.

Second row 5.0 Here's another one. Note the blank line between rows.

---

Grid tables

Allows multiline, and alignment, but visual studio does not like it, and you still have to count those spacees

+---------------+---------------+--------------------+ | Fruit | Price | Advantages | +===============+==============:+====================+ | Bananas | $1.34 | - built-in wrapper | | | | - bright color | +---------------+---------------+--------------------+ | Oranges | $2.10 | - cures scurvy | | | | - tasty | +---------------+---------------+--------------------+ | Durian | $22.10 | - king of fruits | +---------------+---------------+--------------------+

Alignments can be specified as with pipe tables, by putting colons at the boundaries of the separator line after the header.

+------------+---------+---------------------+ | Left | Right | Centered | +:===========+========:+:===================:+ | Bananas | $1.34 | - built-in wrapper | | | | - bright color | +------------+---------+---------------------+ | Durian | $22.10 | - king of fruits | +------------+---------+---------------------+

For headerless tables, the colons go on the top line instead:

+--------------:+:--------------+:------------------:+ | Right | Left | Centered | +---------------+---------------+--------------------+