active-markdown

A tool for generating reactive documents from markdown source.

Active Markdown, v0.1.0

Active Markdown is a tool for making reactive documents — in the vein of Tangle — using a plain text markdown source, with a special notation for adding interactive controls and variables. The logic is determined by the contents of the code blocks, which is actually executed on-the-fly to update the variables.

A sample raw Active Markdown file looks like this:

# St Ives

An old riddle.

> As [I]{travelers: we or I} [was]{verb} going to *St Ives*  
> I met a man with [7 wives]{wives: 1..10}  
> Every wife had [7 sacks]{sacks: 1..10}  
> Every sack had [7 cats]{cats: 1..10}  
> Every cat had [7 kits]{kits: 1..10}  
> Kits, cats, sacks, wives  
> How many were going to St Ives?

    total_sacks = @wives * @sacks
    total_cats  = total_sacks * @cats
    total_kits  = total_cats * @kits
    man         = 1

    if @travelers
        narrator = 2
        @verb = 'were'
    else
        narrator = 1
        @verb = 'was'

The first guess is often [2753]{first_guess}…

    @first_guess = man + @wives + total_cats + total_kits + narrator

…but the correct answer is **[1]{answer}**.

    @answer = narrator

(rendered form »)

…where the [7]{wives: 1..10} gets replaced with a slider from 1 to 10, defaulting at 7. Whenever the value of one of the variables is changed, the code in the given code block is executed using the current state of all the variables. Then, the variables are updated with the new state.

The notation is similar to the syntax for images and links, but when combined with some UI code by the rendering command, creates a rich, interactive and reactive document. Inspired by literate CoffeeScript and Tangle, the goal is a lightweight format for specifying interaction without requiring the creation of a webapp. Also, the document exposes its logic directly, and allows for easy modification and experimentation.

[text value]{var_name}                  - interpolated variable (readonly)
[5]{var_name: 1..10}                    - slider from 1 to 10, default 5
[this]{var_name: this or that}          - toggle switch between `this` or `that`

The code blocks have access to these variables under the top-level this object. Also, the code blocks are editable, and recompiled for every execution, allowing for additional interactivity. (Note: the code in the code blocks MUST be CoffeeScript.)

This is still experimental, and very rough around the edges. For more information, see the initial writeup.

  1. Install:

    $ npm install -g active-markdown
    
  2. Compile an Active Markdown-formatted file:

    $ activemd file.md
    Compiled file.md -> file.html
    

    The command can generate a sample file for you to use and examine.

    $ activemd --sample
    Generating sample: sample.md
    
    $ activemd --sample > some_name.md
    Generating sample
    
  3. Open the compiled file in your favorite browser:

    $ open file.html
    

The basic usage is activemd FILE. This will compile a markdown file with the Active Markdown notation into an HTML file

activemd [options] FILE(S)

Options:

  • -l --local FILE(S) Create local copies of the asset files, relative to the specified source file(s). By default, the assets used are remote, specifically:

    http://activemarkdown.org/viewer/activemarkdown-X.Y.Z-min.css
    http://activemarkdown.org/viewer/activemarkdown-X.Y.Z-min.js
    
  • -i --inline FILE(S) Inline the asset files in the template. Similar to --local, but includes the content of the assets in the actual output file, creating a single, self-contained Active Markdown viewer file.

  • --sample Generate a sample file that contains all of the possible controls in various configurations.

A read-only output of the current value of the specified variable <var_name>. The text is the default value, though it will be replaced when the HTML version loads.

[<default text>]{<var_name>}

  • String

    [text content]{var_name}

A number adjustable by slider. The number MAY have a display precision specified. The slider can be set to a minimum and/or maximum, and have a step value. The text is parsed, and the first number in the text becomes the output value. The remaining text is added to the template, allowing for units and other descriptive text to be included in the control.

A range MUST be specified, but MAY be infinite in both directions. The range is specified using the CoffeeScript-style dots, where .. is inclusive and ... excludes the end. ie, 1..4 is the range 1 <= n <= 4, while 1...4 is 1 <= n < 4. Infinite is expressed by omitting the number, so 1... is from 1 to infinity, and ... is from -infinity to infinity.

Specifying a display precision MAY be done using the default number value in the text. 200. formats to 0 decimal places. 200.000 formats to 3 decimals. If not specified, the value is unformatted.

Numbers MAY use the constants in Math and combine them with a coefficient, eg 2pi or 0.5pi, which is treated as n * Math.PI. This can be done in the range min or max, or in the step. The constants MUST be one of e, pi, ln2, ln10, log2e, log10e, sqrt1_2, sqrt2, (uppercase or lowercase).

[* <number>.<decimal*> *]{<var_name>: <min>..<exclusive><max> by <step>}

The default value MAY contradict any min or max set by the range. However, upon first interaction, the value will be brought within the range.

  • Number, precision of 1, slider step by 10, "#{value.toFixed(0)} calories"

    [200. calories]{calories: 10..100 by 10}

  • Number, precision of 0.1, slider step by 0.1, not inclusive, "#{value.toFixed(1)} calories"

    [80.0 calories]{calories: 10...100 by 0.1}

  • Number, no precision, slider step by 1, no slider max, "#{value} calories"

    [50 calories]{calories: 0..}

  • Number, precision of 0.0001, slider step by 0.01, "#{value.toFixed(4)}"

    [4.0000]{num: pi..2pi by 0.01}

  • Number, precision of 0.01, slider step by 1, no min/max, "over $#{value.toFixed(2)} per day"

    [over $200.00 per day]{payment: ..}

A boolean flag that has a value of true, false, or . The true and false values can be labeled. If the label is present in the text, that value becomes the default value. Otherwise, the value is .

[* <true_label or false_label or *> *]{<var_name> <true_label> or <false_label>}

  • Boolean,"#{value}", default = undefined

    [pick one]{some_flag: true or false}

  • Boolean,"when #{value}", default = true

    [when true]{some_flag: true or false}

  • Boolean, true label = "on", false label = "off", "#{label} deck"

    [on deck]{some_flag: on or off}

Note: graphs, visualizations, and math helpers are in the works.

Thanks to J Voight, Alex Cabrera, John Debs, and Supriyo Sinha for help with the notation.

The concept and controls are heavily influenced by Bret Victor’s Tangle library for creating reactive documents.

  • You? - Active Markdown is still very experimental, and input on the notation, bugs, use cases, control elements, and anything else is very welcome.

Unless otherwise noted, this software is Unlicensed, aka Public Domain. See /UNLICENSE for more information.