A literate programming compiler. Write your program in markdown. This is the core library and does not know about files.
Last updated 5 months ago by jostylr .
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Write your code anywhere and in any order with as much explanation as you like. literate-programming will weave it all together to produce your project.

This is a modificaiton of and an implementation of Knuth's Literate Programming technique. It is perhaps most in line with noweb.

It uses markdown as the basic document format with the code to be weaved together being markdown code blocks. GitHub flavored code fences can also be used to demarcate code blocks. In particular, commonmark is the spec that the parsing of the markdown is used. Anything considered code by it will be considered code by literate programming.

This processing does not care what language(s) your are programming in. But it may skew towards more useful for the web stack.

This is the core library that is used as a module. See -cli for the command line client. The full version has a variety of useful standard plugins ("batteries included").


This requires node.js and npm to be installed. See nvm for a recommend installation of node; it allows one to toggle between different versions. This has been tested on node.js .10, .12, and io.js. It is basic javascript and should work pretty much on any javascript engine.

Then issue the command:

npm install literate-programming-lib

Since this is the library module, typically you use the client version install and do not install the lib directly. If you are hacking with modules, then you already know that you will want this in the package.json file.

Using as a module

You can use Folder = require('literate-programming-lib'); to get a constructor that will create what I think of as a folder. The folder will handle all the documents and scopes and etc.

To actually use this library (as opposed to the command line client), you need to establish how it fetches documents and tell it how to save documents. An example is below. If you just want to compile some documents, use the command line client and ignore this. Just saying the following is not pretty. At least, not yet!

The thing to keep in mind is that this library is structured around events using my event-when library. The variable gcd is the event emitter (dispatcher if you will).

var fs = require('fs');
var Folder = require('literate-programming-lib');
var folder = new Folder();
var gcd = folder.gcd;
var colon = folder.colon;

gcd.on("need document", function (rawname) {
    var safename = colon.escape(rawname);
    fs.readfile(rawname, {encoding:'utf8'},  function (err, text) {
        if (err) {
            gcd.emit("error:file not found:" + safename);
        } else {
            folder.newdoc(safename, text);

gcd.on("file ready", function(text, evObj) {
    var filename = evObj.pieces[0]; 
    fs.writefile(filename, text);


This last line should start the whole chain of compilation with being read in and then any of its files being called, etc., and then any files to save will get saved.

The reason the lib does not have this natively is that I separated it out specifically to avoid requiring file system access. Instead you can use any kind of function that provides text, or whatever. It should be fine to also use folder.newdoc directly on each bit of text as needed; everything will patiently wait until the right stuff is ready. I think.

Note that live code can be run from a literate program as well. So be careful!


Let's give a quick example of what a sample text might look like.

# Welcome

So you want to make a literate program? Let's have a program that outputs
all numbers between 1 to 10.

Let's save it in file count.js

[count.js](#Structure "save:")

## Structure 

We have some intial setup. Then we will generate the array of numbers. We
end with outputting the numbers. 

    var numarr = [], start=1, end = 11, step = 1;



## Output 

At this point, we have the array of numbers. Now we can join them with a
comma and output that to the console.

    console.log("The numbers are: ", numarr.join(", ") );

## Loop

Set the loop up and push the numbers onto it. 

    var i;
    for (i = start; i < end; i += step) {

A full example of a literate program is in this repository. It compiles to this library.

Document syntax

A literate program is a markdown document with some special conventions.

The basic idea is that each header line (regardless of level, either atx # or seText underline ) demarcates a full block. Code blocks within a full block are the bits that are woven together.

Code Block

Each code block can contain whatever kind of code, but there is a primary special syntax.

_"Block name" This tells the compiler to compile the block with "Block name" and then replace the _"Block name" with that code.

Note the the allowed quotes are double, single, and backtick. Matching types are expected. And yes, it is useful to have three different types.

The full syntax is something of the form _"scope name::block name:minor block name | cmd arg 1, arg 2 | cmd2 |cmd3 ..." where the scope name allows us to refer to other documents (or artificial common scopes) and the commands run the output of one to the input of the other, also taking in arguments which could they themselves be block substitutions.

Note that one can also backslash escape the underscore. To have multiple escapes (to allow for multiple compiling), one can use \#_" where the number gets decremented by one on each compile and, when it is compiled with a 0 there, the sub finally gets run.

A block of the form _":first" would look for a minor block, i.e., a block that has been created by a switch directive. See next section.

One can also visually hide parts of the document, without it being hidden to the compiler, by using html comments. If the start of a line is <!--+ then it will strip that and the next occurrence of --> before doing the markdown compiling.


A directive is a command that interacts with external input/output. Just about every literate program has at least one save directive that will save some compiled block to a file.

The syntax for the save directive is

[file.ext](#name-the-heading "save: encoding | pipe commands")  


  • file.ext is the name of the file to save to
  • name-the-heading is the heading of the block whose compiled version is being saved. Spaces in the heading get converted to dashes for id linking purposes. Colons can be used to reference other scopes and/or minor blocks. In particular, #:jack will refernce the jack minor in the current heading block where the save directive is located.
  • save: is there to say this is the directive to save a file
  • encoding is any valid encoding of iconv-lite. This is relevant more in the command line module, but is here as the save directive is here.
  • pipe commands optional commands to process the text before saving. See next section.

For other directives, what the various parts mean depends, but it is always

[some](#stuff "dir: whatever")  

where the dir should be replaced with a directive name. If dir is absent, but the colon is there, then this demarcates a minor block start.


One can also use pipes to pipe the compiled text through a command to do something to it. For example, _"Some JS code | jshint" will take the code in block some JS code and pipe it into the jshint command which can be a thin wrapper for the jshint module and report errors to the console. That command would then return the text in an untouched fashion. We can also use pipe commands to modify the text.

Commands can be used in block substitutions, minor block directive switches, and other directives that are setup to use them such as the save and out directive:
[code.js](#some-js-code "save: | jstidy) will tidy up the code before storing it in the file code.js.

If you want your own directive to process pipes, see the save directive in Pay particular attention to the "process" and "deal with start" minor blocks. The functionality of pipe parsing is in the doc.pipeParsing command, but there are events that need to be respected in the setup.

Commands take arguments separated by commas and commands end with pipes or the block naming quote. One can also use a named code block as an argument, using any of the quote marks (same or different as surround block name). To escape commas, quotes, pipes, underscores, spaces (spaces get trimmed from the beginning and ending of an argument), newlines, one can use a backslash, which also escapes itself. Note that the commonmark parser will escape all backslash-punctuation combinations outside of code blocks. So you may need a double backslash in directive command pipings.

You can also use \n to pu ta newline in line or \u... where the ... is a unicode codepoint per JavaScript spec implemented by string.fromcodepoint.

Minor Block

Finally, you can use distinct code blocks within a full block. If you simply have multiple code blocks with none of the switching syntax below, then they will get concatenated into a single code block.

You can also switch to have what I call minor blocks within a main heading. This is mainly used for small bits that are just pushed out of the way for convenience. A full heading change is more appropriate for something that merits separate attention.

To create a minor block, one can either use a link of the form [code name]() or [code name](#whatever ":|cmd ...") Note this is a bit of a break from earlier versions in which a link on its own line would create a minor block. Now it is purely on the form and not on placement.

Example: Let's say in heading block ### Loopy we have [outer loop]() Then it will create a code block that can be referenced by _"Loopy:outer loop".

Note: If the switch syntax is [](#... ":|...") then this just transforms whatever is point to in href using the pipe commands. That is, it is not a switch, but fills in a gap for main blocks not having pipe switch syntax. The key is the empty link text.


One use of minor blocks is as a templating mechanism.

## Top

After the first compile, the numbers will be decremented, but the blocks
will not be evaluated.



This is now a template. We could use it as

[jack](# "store:| compile basic ")

[happy.txt](#jack "save:| compile great")
[sad.txt](# "save:| compile basic | compile grumpy")

# Basic

    Greetings and Salutations



# Great


    You are great.

# Grumpy


    You are grumpy.

# Middle


    You are okay.

## Another



[middle.txt](# "save:| sub $2, middle | compile basic")

This would produce the files:


Greetings and Salutations

You are great.



Greetings and Salutations

You are grumpy.



Greetings and Salutations

You are okay.


Note that you need to be careful about feeding in the escaped commands into other parsers. For example, I was using Pugs to generate HTML structure and then using this templating to inject content (using markdown). Well, Pugs escapes quotes and this was causing troubles. So I used backticks to delimit the block name instead of quotes and it worked fine. Be flexible.

Nifty parts of writing literate programming

  • You can have your code in any order you wish.

  • You can separate out flow control from the processing. For example,

      if (condition) {
      } else {

    The above lets you write the if/else statement with its logic and put the code in the code blocks truth and beauty. This can help keep one's code to within a single screenful per notion.

  • You can write code in the currently live document that has no effect, put in ideas in the future, etc.

  • You can "paste" multiple blocks of code using the same block name. This is like DRY, but the code does get repeated for the computer. You can also substitute in various values in the substitution process so that code blocks that are almost the same but with different names can come from the same root structure.

  • You can put distracting data checks/sanitation/transformations into another block and focus on the algorithm without the use of functions (which can be distracting).

  • You can process the blocks in any fashion you want. So for example, to create a JSON object, one could use a simpler setup appropriate for the particular data and then transform it into JSON. It's all good.

  • This brings DSL and grunt power, written in the same place as your code. It is really about coding up an entire project.

  • Getting the length of functions right is difficult. Too short functions, and boilerplate and redirection becomes quite the bother. Too long, and it is hard to understand what all a function is doing. Too long and we lose composability. Too short, the chain of composing them becomes too long. Literate programming can help somewhat in that we can have longer functions and still have it understood. We could also potentially use the litpro blocks again allowing for some composability though that that should be rare. I think the rule of thumb is that if breaking it up seems good from a usability stance, do it. If breaking it up is more about keeping a function to a readable length, use litpro blocks. Another advantage of using litpro blocks is that we get the benefit of small parts when coding, but when debugging, we can see a much larger flow of code all at once in the compiled version.

I also like to use it to compile an entire project from a single file, pulling in other literate program files as needed. That is, one can have a command-and-control literate program file and a bunch of separate files for separate concerns. But note that you need not split the project into any pre-defined ways. For example, if designing a web interface, you can organize the files by widgets, mixing in HTML, CSS, and JS in a single file whose purpose is clear. Then the central file can pull it all in to a single web page (or many) as well as save the CSS and JS to their own files as per the reommendation, lessing the CSS, tanspiling ES6, linting, and minifying all as desired. Or you could just write each output file separate in its own litpro document.

It's all good. You decide the order and grouping. The structure of your litpro documents is up to you and is independent of the needed structures of the output.

Directives vs commands vs subcommand

Directives affect the flow of the literate program itself, such as defining commands, saving output, or directly storing values. Commands transform incoming text or other input. Subcommands create useful arguments to commands.

Directives can be thought of as procedures, commands as methods on the input, and subcommands as functions. And indeed, directives do not compose in the sense of returning a value. Commands are written like the chain syntax, with what is on the left being evaluated first. Subcommands are written with typical function syntax, with what is on the right being evaluated first.

Built in directives

There are a variety of directives that come built in.

  • Save [filename](#start "save:options|commands") Save the text from start into file filename. The options can be used in different ways, but in the command client it is an encoding string for saving the file; the default encoding is utf8.

  • Store [name|value](#start "store:value|...") If the value is present, then it is sent through the pipes. If there is no value, then the #start location is used for the value and that gets piped. The name is used to store the value. You can also use the pipe syntax in the linkname part for the value instead. This dominates over the start or option value. A little bit easer for the reader to see in rendered form.

  • Log Same as store, except instead of storing it in the doc, it logs it to console. Same exact syntax.

  • Transform [des|name](#start "transform:|...) or [des|name](#start ":|..."). This takes the value that start points to and transforms it using the pipe commands. Note one can store the transformed values by placing the variable name after a pipe in the link text. The description of link text has no role. For the syntax with no transform, it can be link text that starts with a pipe or it can be completely empty. Note that if it is empty, then it does not appear and is completely obscure to the reader.

  • Load [alias](url "load:options") This loads the file, found at the url (file name probably) and stores it in the alias scope as well as under the url name. We recommend using a short alias and not relying on the filename path since the alias is what will be used repeatedly to reference the blocks in the loaded file. Options are open, but for the command line client it is the encoding string with default utf8. Note there are no pipes since there is no block to act on it.

  • Cd [path](#ignore "cd: load/save") This creates the ability to change directories for either loading or saving. This is relative to the default directory. [](# "cd: load") (or save) will clear the path; it is always good to do that when done. Ideally, this would be a tightly grouped of files (listing like a directory) with the initial change right before the list and the changing back after the list.

  • Define [commandName](#start "define: async/sync/raw/defaults|cmd") This allows one to define commands in a lit pro document. Very handy. Order is irrelevant; anything requiring a command will wait for it to be defined. This is convenient, but also a bit more of a bother for debugging. Anyway, the start is where we find the text for the body of the command. The post colon, pre pipe area expects one of three options which is explained below in plugins.You can also pipe your command definition through pipe commands before finally installing the function as a live function. Lots of power, lots of headaches :)

    • The basic signature of a command is function (input, args, name/callback) where the input is the text being piped in, the args are the arguments array of the command, and name is the name to be emitted when done. The this is the doc.
    • sync. This should return a value which will be used as the text being passed along. You can access name if you like, but it is not useful here.
    • async. Name is a callback function that should be called when done. Standard node signature of (err, data). So put the text in the second slot and null in the first if all is well.
    • raw. Nothing is setup for you. You have to get your hands dirty with the event emitter of the doc. You'll need some good understanding of it. See the sub command definition for inspiration.
    • defaults. The idea is that this is mostly synchronous, but has some default arguments that come from the document and hence it is async for that reason. So we need to create a tag for the emitname, document variable names for default, and the function that is to be called when all is ready. To accomodate this, instead of a function, we should have an array that gets read in: [tag, arg0, arg1, ...., fun] where tag is either a string or a function that takes in the passed in arguments and generates a string, arg0 to arg..., are the default doc variables. It is fine to have some be empty. The final entry should be a function of the same type as the sync functions (return values pass along the input).

    This defines the command only for current doc. To do it across docs in the project, define it in the lprc.js. The commandName should be one word.

  • Compose [cmdname](#useless "compose: cmd1, arg1, ..| cmd2, ...") This composes commands, even those not yet defined. The arguments specified here are passed onto the commands as they are executed. There are no subcommands used in these arguments, but subcommands can be used in the arguments differently. If an argi syntax has $i then that numbered argument when the command is invoked is subbed in. If the argi has @i, then it assumed the incoming argument is an array and uses the next available array element; if the @i appears at the end of the arg list, then it unloads the rest of its elements there. This may be a little klunky and the syntax may change. We also have as special commands in compose: which does nothing but handles two accidental pipes in a row smoothly, ->$i which stores the incoming into the ith variable to use later as a named dollar sign variable, $i-> which sends along the ith variable to the next pipe, ->@i which pushes the value onto the ith element, assuming it is an array (it creates an array if no array is found). There is also a special variant of $i->cmd->$j where if the first arrow is present, then it uses argument i as the input and if the second arrow is present, then it saves the output into argument j, sending the original input on instead of the output.

  • Partial [cmdname](#block "partial: oldcmdname, argplace | pipes...") This takes a command, oldcmdname, and makes a new command, cmdname, by replacing an argument slot, argplace zero-based, with whatever the block and pipes result in.

  • Subcommand [subcommandname](#cmdName "subcommand:") This defines subcommandname (one word) and attaches it to be active in the cmdName. If no cmdName, then it becomes available to all commands.

  • Blocks on/off [off](# "block:") Stops recording code blocks. This is good when writing a bunch of explanatory code text that you do not want compiled. You can turn it back on with the [on](# "block:") directive. Directives and headings are still actively being run and used. These can be nested. Think "block comment" sections. Good for turning off troublesome sections.

  • Eval [des|name](# "eval:) Whatever block the eval finds itself, it will eval. It will eval it only up to the point where it is placed. This is an immediate action and can be quite useful for interventions. The eval will have access to the doc object which gives one access to just about everything else. This is one of those things that make running a literate progamming insecure. The return value is nonexistent and the program will not usually wait for any async actions to complete. If you put a pipe in the link name text, then the anything after the pipe will become a name that the variable ret will be stored in.

  • Ignore [language](# "ignore:") This ignores the language code blocks. For example, by convention, you could use code fence blocks with language js for compiled code and ignore those with javascript. So you can have example code that will not be seen and still get your syntax highlighting and convenience. Note that this only works with code fences, obviously. As soon as this is seen, it will be used and applied there after.

  • Out [outname](#start "save:|commands") Sends the text from start to the console, using outname as a label.

  • New scope [scope name](# "new scope:") This creates a new scope (stuff before a double colon). You can use it to store variables in a different scope. Not terribly needed, but it was easy to expose the underlying functionality.

  • Push [var name |value](#start "push: |...") This takes the stuff in start, throws it through some pipes, and then stores it as an item in an array with the array stored under var name. These are stored in the order of appearance in the document. The optional pipe syntax after var name will yield the value that starts and we ignore #start in that case.

  • h5 [varname](#heading "h5: opt | cmd1, ...") This is a directive that makes h5 headings that match heading act like the push above where it is being pushed to an array that will eventually populate varname. It takes an optional argument which could be off to stop listening for the headings (this is useful to have scoped behavior) and full which will give the event name as well as the text; the default is just the text.

  • Link Scope [alias name](# "link scope:scopename") This creates an alias for an existing scope. This can be useful if you want to use one name and toggle between them. For example, you could use the alias v for dev or deploy and then have v::title be used with just switching what v points to depending on needs. A bit of a stretch, I admit.

  • Monitor [match string](# "monitor:") This is a bit digging into the system. You can monitor the events being emitted by using what you want to match for. For example, you could put in a block name (all lower cased) and monitor all events for that. This gets sent to doc.log which by default prints to console.log. If you use \: in the match string, this becomes the triple colon separator that we use for techinical reasons for block:minor name syntax. This directive's code gives a bit of insight as to how to get more out of the system.

  • If [...](... "if: flag; directive:...") If flag holds true (think build flag), then the driective is executed with the arguments as given. A couple of great uses are conditional evaling which allows for a great deal of flexibility and conditional block on/off which may be useful if there is extensive debugging commands involved.

  • Flag [flag name](# "flag:") This sets the named flag to true. Note there is no way to turn a flag off easily.

  • Version [name](# "version: number ; tagline") This gives the name and version of the program. Note the semicolon separator. Saves g::docname, g::docversion, g::tagline.

  • npminfo [author name](github/gituser "npminfo: author email; deps: ; dev: " ) This takes in a string for some basic author information and dependencies used. To add on or modify how it handles the deps, dev, etc., modify the types object on Folder.directives.npminfo. Saves g::authorname, g::gituser, g::authoremail, g::npm dependencies, g::npm dev dependencies.

Built in commands

Note commands need to be one word and are case-sensitive. They can be symbols as long as that does not conflict with anything (avoid pipes, commas, colons, quotes).

  • eval code, arg1,... The first argument is the text of the code to eval. In its scope, it will have the incoming text as the text variable and the arguments, which could be objects, will be in the args array. The code is eval'd (first argument). The code text itself is available in the code variable. The variable text is what is passed along. This should make for quick hacking on text. The doc variable is also available for inspecting all sorts of stuff, like the current state of the blocks. If you want to evaluate the incoming text and use the result as text, then the line text = eval(text) as the first argument should work.

  • async (async eval) code1, code2, ... Same deal as eval, except this code expects a callback function to be called. It is in the variable callback. So you can read a file and have its callback call the callback to send the text along its merry way.

  • evil While the eval commands thinks of the first argument as code acting on the incoming text, its twin evil thinks of the incoming text as the code and the arguments as just environment variables. The value returned is the variable ret which defaults to the original code.

  • funify This assumes the incoming text is a function-in-waiting and it evals it to become so. This is great if you want to do a .map or if you just want to mess with stuff. .call , args.. will call the function and return that result.

  • compile block, minor1, val1, minor2, val2,... This compiles a block of text as if it was in the document originally. The compiled text will be the output. The first argument gives the names of the blockname to use if short-hand minor blocks are encountered. This is useful for templating. If no blockname is given, then the current one is used. Any further arguments should be in pairs, with the second possibly empty, of a minor block name to fill in with the value in the second place.

  • sub

    A: Replaces parts of incoming text.

    S: str -> key1, val1, key2, val2, ... -> str, str-> regexp, replacement str/fun -> str

    This replaces key# in the text with val#. The replacement is sorted based on the length of the key value. This is to help with SUBTITLE being replaced before TITLE, for example, while allowing one to write it in an order that makes reading make sense. This is a bad, but convenient idea.

    Recommend just using one pair at a time as commands can be piped along.

    Alternate signature regexp, replacement str/func. This does a regular expression replacement where the first is a reg ( reg(str, flags) ) that acts on the string and replaces it using the usual javascript replacement syntax for the second.

    The regex syntax can be part of pair sequences. In accordance with shorter first, regex's which typically are epansive, will go last, but amongst regex's, the order of processing is preserved. Recommendation is to not mix in multiple pairs with regexs.


    #basic, string

  • store variable name This stores the incoming text into the variable name. This is good for stashing something in mid computation. For example, ...|store temp | sub THIS, that | store awe | _"temp" will stash the incoming text into temp, then substitute out THIS for that, then store that into awe, and finally restore back to the state of temp. Be careful that the variable temp could get overwritten if there are any async operations hanging about. Best to have unique names. See push and pop commands for a better way to do this.

  • clear variable name. This removes the variable name and passes along the input. The input has no impat on this.

  • log This will output a concatenated string to doc.log (default console.log) with the incoming text and the arguments. The first argument is treated as an idenitifer in the output. This is a good way to see what is going on in the middle of a transformation.

  • raw start, end This will look for start in the raw text of the file and end in the file and return everything in between. The start and end are considered stand-alone lines.

  • trim This trims the incoming text, both leading and trailing whitespace. Useful in some tests of mine.

  • filter This will filter an array or object into a lesser object, based on what the rest of the arguments are. If the input is an object, then it will take the rest of the arguments as either:

    • type string: explicit keys to keep.
    • type regexp: keys must match the regexp to be kept.
    • type function: a function that takes in the key and value returns the boolean true if the key, value should be added.
    • true: if the boolean true (or no argument at all is supplied) then all this essentially copies the object.

    It filters the object based on these criteria and returns the new object.

    For an array, it is similar except an array is returned.

    • either actual number or one that parses into it. This pushes the

      entry at the number onto the new array.
    • '#:#' will slice it between the two numbers.
    • 'ax + b' b is the starting value (negative counts from the end) while a is the increment to add (negative goes down).
    • type function takes in the value and index and returns true if the value should be added.
    • true adds a whole copy of the array; also default if nothing is provided.
  • join This will concatenate the incoming text and the arguments together using the first argument as the separator. Note one can use \n as arg1 and it should give you a newline (use \\n if in a directive due to parser escaping backslashes!). No separator can be as easy as |join ,1,2,....

    This also does double duty as something entirely different. If the input is an object or an array, then it first filters it according to the arguments, just as in the filter command, and then joins the results with the first argument as the join separator. For objects, if the keys are a group (such as regexp matching), then they will be sorted alphabetically first before joining.

  • cat The arguments are concatenated with the incoming text as is. Useful for single arguments, often with no incoming text.

  • echo echo This is output This terminates the input sequence and creates a new one with the first argument as the outgoing.

  • get get blockname This is just like using _"blockname" but that fails to work in compositions. So get is its replacement. This ignores the input and starts its own chain of inputs.

  • array array a1, a2, ... This creates an array out of the input and arguments.

  • . . propname, arg1, arg2,... This is the dot command and it accesses property name which is the first argument; the object is the input (typically a string, but can be anything). If the property is a method, then the other arguments are passed in as arguments into the method. For the inspirational example, the push directive creates an array and to join them into text one could do | . join, \,. There is also an alias so that any .propname as a command works. For example, we could do | .join \, above. This avoids forgetting the comma after join in the prior example.

  • - - propname, arg1, arg2,... This is the dash command and it accesses the utility property which is the first argument; the object is the input (typically a string, but can be anything). It calls the relevant command with that method.

    Each object in the Folder.dash has the form cmdname: [object with methods, num] where the command name is the name to be called (such as lodash and the methods should be on the called object, such as require('lodash') and the num order the search, with lower numbers coming first.

  • push Simply pushes the current state of the incoming text on the stack for this pipe process.

  • pop Replaces the incoming text with popping out the last unpopped pushed on text.

  • if boolean, cmd, arg1, arg2, .... If the boolean is true, then the command will execute with the given input text and arguments. Otherwise, the input text is passed on. This is usefully paired with the subcommand boolean asks. For example ?and(?flag(left),?flag(right)) will execute theifif bothleftandright` are flagged.

  • ifelse arr(bool, cmd, arg1, arg2, ...), arr(bool2, cmd2, arg21, arg22, ...), ... This expects arrays of the above form as arguments. It works through the conditions until it finds a true value and then it executes the command. If none are found, then it passes along the input text.

  • when name1, name2, ... This takes in the event names and waits for them to be emitted by done or manually with a doc.parent.done.gcd.once(name, "done"). That would probably be used in directives. The idea of this setup is to wait to execute a cli command for when everything is setup. It passes through the incoming text.

  • done name This is a command to emit the done event for name. It just passes through the incoming text. The idea is that it would be, say, a filename of something that got saved.

  • arrayify This takes the incoming text and creates an array out of it. The first argument is an object with keys sep to know what to split on, esc to escape the separator and itself, trim a boolean that will trim the text for each entry. The defaults are newline, backslash, and true, respectively. You can also pass them as the first, second, and third argument, respectively. Note that this assumes that both sep and esc are single characters. You can have the usual block substitutions, of course, but it might be safer to escape the block and run it through compile, e.g., | arrayify | .mapc compile. This also allows nesting of objects. To get a string representation of the array, call | .toString.

  • objectify This takes the incoming text and creates an object out of it. The first argument is an object with keys key to know what to split on for the key, val to split on for the end of the value, esc to escape the separator and itself, trim a boolean that will trim the value for each entry; keys are automatically trimmed. The defaults are colon, newline, backslash, and true, respectively. Note that this assumes that all the characters are single characters. You can have the usual block substitutions, of course, but it might be safer to escape the block and run it through compile, e.g., | objectify | .mapc compile. This also allows nesting of objects. Call |.toString() to get a string.

  • regify Turns the incoming input into a regular expression. First argument are the flags; if none, g is assumed, but if some flags are specificed one should add g. If no global needed use, '-'.

  • ife This takes a snippet of code and creates an immediate function execution string for embedding in code. the arguments become the variable names in both the function call and the function definition. If an equals is present, then the right-hand side is in the function call and will not be hidden from access in the ife.

  • caps This is a command that tries to match caps and replace them. The idea comes from wanting to write M W>900px and get @media (min-width:900px). This does that. By passing in a JSON object of possible matches as argument or setting the caps local object to an object of such matches, you can change what it matches. But it only will match a single character (though unicode is fine if you can input that).

  • assert This asserts the equality of the input and first argument and if it fails, it reports both texts in a log with the second argument as a message. something | assert _"else", darn that else. This is a way to check that certain things are happening as they should.

  • wrap This wraps the incoming text in the first and second argument: some text | wrap <, >" will result in<some text>`.

  • js-string This breaks the incoming text of many lines into quoted lines with appropriate plus signs added. The first argument allows for a different quote such as '. The double quote is default. Also q and qq generates single and double quotes, respectively.

  • html-wrap This takes the incoming text and wraps it in a tag element, using the first argument as the element and the rest of the arguments as attributes. An equals sign creates an attribute with value, no equals implies a class. An attribute value will get wrapped in quotes. text-> | html-wrap p, data, pretty, data-var=right will lead to <p class="data pretty" data-var="right">text</p>

  • html-table This requires an array of arrays; matrix is good. The first argument should either be an array of headers or nothing. It uses the same argument convention of html-wrap for the rest of the arguments, being attributes on the html table element. We could allow individual attributes and stuff on rows and columns, but that seems best left to css and js kind of stuff. Still thinking on if we could allow individual rows or entries to report something, but that seems complicated.

  • html-escape This escapes <>& in html. It is mainly intended for needed uses, say in math writing. Very simple minded. One can modify the characters escaped by adding to Folder.plugins.html_escape. This is actually similar to caps and snippets.

  • html-unescape The reverse of html-escape, depending on what the symbols are in plugins.html_unescape.

  • snippets (alias s ). This is a function for things that are easily named, but long to write, such as a cdn download script tag for a common js library, say jquery. s jquery could then do that. Currently, there are no default snippets. To load them, the best bet is in the lprc.js file and store the object as Folder.plugins.snipets = obj or, if you are feeling generous, one could do Folder.merge(Folder.plugins.snippets, obj);. This is really a stand-alone command; incoming text is ignored.

    In writing a snippet, it can be a function which will take in the arguments. Alternatively, you can sprinkle ARG#||...| in your code for the Argument with numner # and the pipes give an optional default; if none, then ARG# is eliminated. So ARG0||1.9.0| yields a default of 1.9.0. Pipes cannot be in the default

    Be careful that the first argument is the snippet name.

  • #/#name This is just a comment. For special-character free text, one can just write it, but if one wants to include special characters, use ec('...'). Example # This is a comment or #dude this is a comment. This latter form will store the current state into doc.comments.

  • cmds This creates a sequence of commands to execute, most likely used with if-else since a single pathway is covered by the usual pipe syntax. The form is cmds cmd1, array of args for 1, cmd2, args for 2, e.g., cmds sub, arr(awe, dud), cat, arr(dude, what)... If it is just one argument, then the array is not needed (if it is just one argument and that is an array, wrap that in an array)).

  • mapc or * with cmd, arg1, ... This takes the input and applies cmd to each, if array or obj. Otherwise, just appleis command to whole input. *cmds arr(...), arr(...) allows a sequence of commands to happen. For the object, if the args contains *KEY*, then that gets replaced by the key under consideration.

  • forin The args are function f (val, key, ret, input), initial value, sort order. This iterates over the input object.

    If the input is not an array or object, then f is called on the input itself as val with a key of an empty string, and the ret is just the initial value.

    The return value of f is used in the third plave of the next loop. If it is undefined, null is passed in.

    All functions should be synchronous. All values will be visited; there is no way to break out of the loop though one could have the function do nothing if the ret value was a particular kind (say, looking for false values, it starts true and if it becomes false, then it just returns that for all later ones). This is not designed for large number of keys.

    The sort should be a comparison function that expects the following arguments: key1, key2, value1, value2, input. Alternatively, it can send in the strings key or value to sort the order by intrinsic key or value meaning. Note that value needs to be natively comparable in some meaningful sense if value is sent in.

  • pget Gets the property named by the arguments.

  • pset Sets the property named by the arguments with the last argument being the value. May create objects and arrays as needed.

  • pstore This stores the input into the first argument (should be object or array) using the rest of the arguments to define. This returns the value.

  • toJSON Returns a JSON representation of input. Uses JSON.stringify and passes in the first two args (whitelist, spaces) to allow full features.

  • fromJSON Returns an object from a JSON representation. Uses JSON.parse and passes in first argument (reviver function) if present.

  • anon The first argument should be a function or string that can be converted into a function of command form, namely the arguments are input, arguments and the this is doc though that is also in a closure if it is a string evaluated. The function should be synchronous and return the value to send on.

  • minors This converts the input from an array into an object, using the arguments as the keys. If there is a mismatch in length, than the shorter is used and the rest is discarded. If the input is not an array, then it becomes the sole value in the object returned with key as first argument or empty string.

  • templating This expects an object as an input. Its keys will be minor block names when compiling the template given by the first argument. It will send along the compiled text.

  • merge Merges arrays or objects.

  • clone Clones an array or object.

  • apply This applies a function or command to a property of an object and replaces it. Clone first if you do not want to replace, but have a new. The first arguments is the key, the second is the commnd string or function, and the rest are the args to pass in. It returns the object with the modified property.

  • matrixify This takes in some text and splits into a two dimensional array using the passed in separators. The first separator divides the columns, the second divides the rows. The result is an array each of whose entries are the rows. There is also an escape character. The defaults are commas, newlines, and backslashes, respectively. The escpae character escapes the separators and itself, nothing else. There is also a boolean for whether to trim entries; that is true by default. Pass in f() in the fourth argument if not desired. All the characters should be just that, of length 1.

    This returns a matrix (prototyped) that has the properties:

    • rows Iterates a function over the rows. If an array is returned, it replaces the row.
    • cols Iterates a function over the cols and will also replace the columns if an array is returned.
    • transpose This returns a new matrix with flipped rows and columns.
    • trim This trims the entries in the matrix, returning the original.
    • num This converts every entry into a number, when possible.
    • clone This creates a copy.
    • traverse This runs through the matrix, applying a function to each entry, the arguments being element, inner index, outer index, the row object, the matrix.
    • equals This takes in a second matrix and checks if they are strictly equal.
    • print This prints the matrix using the passed in row and col separator or using the property

Built-in Subcommands

With command arguments, one can run commands on arguments to get them in some appropriate form or use, including passing in objects or arrays. You can use them as cmd a, subcmd(arg1, arg2, arg3) would have subcmd acting on the args and the result of that would be the argument place The a would be passed into cmd as the first argument, but anything might get passed into cmd by subcmd's return value. It could also store an object into a state for configuration.

There are several built-in subcommands. Note that these are case insensitive.

  • ec or echo This expects a quote-delimited string to be passed in and will strip the quotes. This is useful as the appearance of a quote will mask all other mechanics. So e("a, b and _this") will produce a literal argument of a, b, and _this. Multiple arguments will be stripped and passed on as multiple arguments.
  • join The first entry is the joiner separator and it joins the rest of the arguments. For arrays, they are flattened with the separator as well (just one level -- then it gets messy and wrong, probably).
  • arr or array This creates an array of the arguments.
  • arguments or args Inverse of array. This expects an array and each element becomes a separate argument that the command will see. E.g., cmd arguments(arr(3, 4)) is equivalent to cmd 3, 4. This is useful for constructing the args elsewhere. In particular, args(obj(_"returns json of an array")) will result in the array from the subsitution becoming the arguments to pass in.
  • obj or object This presumes that a JSON stringed object is ready to be made into an object.
  • merge Merge arrays or objects, depending on what is there.
  • kv or key-value This produces an object based on the assumption that a key, value pairing are the arguments. The key should be text. Multiple pairs welcome.
  • act This allows one to do obj, method, args to apply a method to an object with the slot 2 and above being arguments. For example, one could do act( arr(3, 4, 5), slice, 2, 3) to slice the array to [5].
  • .method This is similar to act except that the method is in the name. So the same example would be .slice( arr(3, 4, 5), 2, 3). Also dot(slice, arr(3,4,5), 2, 3).
  • prop or property. This will take the arguments as a property chain to extract the value being pointed to.
  • json This will convert an object to JSON representation.
  • set The presumption is that an object is passed in whose key:values should be added to the command state. gSet does this in a way that other commands in the pipe chain can see it. set(kv(name, val, ...)) would probably be the typical way.
  • get This retrieves the value for the given key argument. gGet does the same for the pipe chain. Multiple keys can be given and each associated value will be returned as distinct arguments.
  • num number This converts the argument(s) to numbers, using js Number function. num(1, 2, 3) will create three arguments of integers. To get an array, use arr(num(1, 2, 3)
  • date Returns a date object. date() returns what the current now is, date(some date string) will return a date object as parsed by Date.
  • ev oreval will evaluate the argument and use the magic ret variable as the value to return. This can also see doc (and doc.cmdName) and args has the arguments post code. Recommend using backticks for quoting the eval; it will check for that automatically (just backticks, can do echo for the others if needed).
  • fun or function evaluates the code as if it is a function and returns that function. Any other arguments are seen in the args closure variable. Just like eval, backticks can be used and should be used to directly quote the function text.
  • log This logs the arguments and passes them along as arguments.
  • true. This returns the true value.
  • false. This returns the false value.
  • null. This returns the null value.
  • reg or regexp Takes in a regular expression string and possibly some flags and returns a regular expression. Defaults to a global flag; pass in - as part of the flags to get non-global.
  • doc. This returns the doc variable. This could be useful in connection to the property method and the log subcommand.
  • skip. This returns no arguments.
  • -fun or dash(fun, ...) will use the functions found in the dash command but as a subcommand. -pad(dude, 5) will pad the string dude to have length 5 using the default spaces (in full where lodash is added to the dash).
  • ?test or bool(test, ...) will apply the test to the arguments. The following are the default tests in the variable doc.booleans:
    • and checks that all are truthy
    • or checks that at least one is truthy`
    • not negates the boolean
    • ===, ==, >, >=, <, <= tests in sequence the relation.
    • !==, != tests all pairs for non-equality.
    • flag looks to see if the passed in strings are flags that have been set.
    • match Takes in a string as first argument and either a string or regular expression to match.
    • type Tests first argument as one of the types that follow (strings).
  • input This returns the incoming input. Should be useful for extraction of information, particularly for boolean tests.
  • type Yields the type of the object in first argument.

To build one's own command, you can attach a function whose arguments will be the arguments passed in. The this is the doc object. The current name (say for scope storing) is in doc.cmdName. This will point to within a whole pipe chunk. Pop off the last part (delimited by triple colon) to get to the whole command scope. The return value will be used as in an argument into the command or another subcommand. If it is an array and the flag args is set to true, then each entry in the array will be expanded into a set of arguments. So instead of 1 argument, several could be returned. If nothing is returned, then no arguments are passed on and it is as if it wasn't there.

h5 and h6

So this design treats h5 and h6 headings differently. They become subheadings of h1-4 headings. So for example, if we have # top and then ##### doc and ###### something then the sections would be recorded as top, top/doc, top/doc/something and we have a path syntax such as ../ which would yield top/doc if placed in top/doc/something. Ideally, this should work as you imagine. See tests/ for the test examples.


This is a big topic which I will only touch on here. You can define commands in the text of a literate program, and we will discuss this a bit here, but mostly, both commands and directives get defined in module plugins or the lprc.js file if need be.

Defining Commands

The define directive allows one to create commands within a document. This is a good place to start getting used to how things work.

A command has the function signature function (input, args, name)-> void where the input is the incoming text (we are piping along when evaluating commands), args are the arguments that are comma separated after the command name, and the name is the name of the event that needs to be emitted with the outgoing text. The function context is the doc example.

A minimal example is

function ( input, args, name) {
    this.gcd.emit(name, input);

We simply emit the name with the incoming text as data. We usually use doc for the this variable. This is the raw option in the define directive.

The default is sync and is very easy.

function ( input, args, name) {
    return input;

That is, we just return the text we want to return. In general, the name is not needed though it may provide context clues.

The third option is an async command. For those familiar with node conventions, this is easy and natural.

function (input, args, callback, name) {
    callback(null, input);

The callback takes in an error as first argument and, if no error, the text to output. One should be able to use this as a function callback to pass into other callback async setups in node.

So that's the flow. Obviously, you are free to do what you like with the text inside. You can access the document as this and from there get to the event emitter gcd and the parent, folder, leading to other docs. The scopes are available as well. Synchronous is the easiest, but asynchronous control flow is just as good and is needed for reading files, network requests, external process executions, etc.

Plugin convention.

I recommend the following npm module conventions for plugins for literate-programming.

  1. litpro-... is the name. So all plugins would be namespaced to litpro. Clear, but short.

  2. Set module.exports = function(Folder, other) The first argument is the Folder object which construts folders which constructs documents. By accessing Folder, one can add a lot of functionality. This access is granted in the command line client before any folder is created.

    The other argument depends on context, but for the command line client it is the parsed in arguments object. It can be useful for a number of purposes, but one should limit its use as it narrows the context of the use.

  3. Define commands and, less, directives. Commands are for transforming text, directives are for doing document flow maipulations. Other hacks on Folder should be even less rare than adding directives.

  4. Commands and directives are globally defined.

  5. Folder.commands[cmd name] = function (input, args, name)... is how to add a command function. You can use Folder.sync(cmdname, cmdfun) and Folder.async to install sync and async functions directly in the same fashion as used by the define directive.

  6. Folder.directives[directive name] = function (args) is how to install a directive. There are no helper functions for directives. These are more for controlling the flow of the compiling in the large. The arg keys are read off from [link](href "directive:input"). Also provided is the current block name which is given by the key cur.

  7. If you want to do stuff after folder and its event emitter, gcd, is created, then you can modify Folder.postInit to be a function that does whatever you want on a folder instance. Think of it as a secondary constructor function.

  8. The Folder has a plugins object where one can stash whatever under the plugin's name. This is largely for options and alternatives. The folder and doc object map to the same object.

Structure of Doc and Folder

To really hack the doc compiling, one should inspect the structure of Folder, folder, and doc. The Folder is a constructor and it has a variety of properties on it that are global to all folders. But it also has several prototype properties that get inherited by the folder instances. Some of those get inherited by the docs as well. For each folder, there is also a gcd object which is the event emitter, which comes from the, ahem, magnificient event-when library (I wrote it with this use in mind). In many ways, hacking on gcd will manipulate the flow of the compiling.

I wrote the folder instance to maintain flexibility, but typically (so far at least), one folder instance per run is typical. Still, there might be a use for it in say have a development and production compile separate but running simultaneously?


These are the properties of Folder that may be of interest.

  • commands. This is an object that is prototyped onto the instance of a folder. Changing this adds commands to all created folder instances.
  • directives. This holds the directives. Otherwise same as commands.
  • reporter. This holds the functions that report out problems. See reporters below. This is not prototyped and is shared across instances.
  • postInit. This does modification of the instance. Default is a noop.
  • sync, async. These install sync and async commands, respectively.
  • defSubCommand. Installs a subcommand.
  • plugins. This is a space to stash stuff for plugins. Use the plugin sans litpr as the key. Then put there whatever is of use. The idea is if you require something like jshint and then want default options, you can put that there. Then in a lprc file, someone can override those options it will be applied across the project.


Each instance of folder comes with its own instances of:

  • docs. Holds all the documents.
  • scopes. Holds all the scopes which are the stuff before the double colon. It includes the blocks from the compiled docs but also any created scopes.
  • reports. This holds all the reports of stuff waiting. As stuff stops waiting, the reports go away. Ideally, this should be empty when all is done.
  • stack. This is for the push and pop of text piping.
  • gcd. This is the event-emitter shared between docs, but not folders. Default actions are added during the instantiation, largely related to the parsing which sets up later. If you want to log what goes on, you may want to look at the event-when docs (makeLog is a good place to start).
  • flags. This holds what flags are present.

and shares via the prototype

  • parse. This parses the text of docs using commonmark spec
  • newdoc. This creates a new document. Kind of a constructor, but simply called as a function. it calls the constructor Doc.
  • colon. We replace colons with a unicode triple colon for emitting purposes of block names (event-when uses colon as separators too). This contains the escape (does replacement), restore (undoes it), and v which is the unicode tripe colon. If the v is replaced entirely, everything should hopefully work just fine with a new separator.
  • createScope. Creating a scope.
  • join. What is used to concatenate code blocks under same block heading. Default is "\n"
  • log. What to do with logging. Defaults to console.log.
  • indicator. An internal use to allow escaping of whitespace in command arguments that would otherwisebe trimmed.
  • wrapSync, wrapAsync. These wrap functions up for command sync, async, but do not install them. Not sure why not install them.
  • subnameTransform. A function that deals with shorthand minor substitutions that avoid using the main block heading. This can be overwritten if you want some custom behavior.
  • reportwaits. This is a function that produces the reports of what is still waiting. Very useful for debugging. This returns an array.
  • simpleReport. This reports on the substitutions that did not get resolved. This returns an array. It also includes any commands that were called but not defined. Subcommands throw errors when not defined, but since commands can be defined later, they will not. Hence this mechanism.
  • Doc. This is the constructor for documents.
  • commands
  • directives
  • plugins

and direct copying from

  • reporters


Each file leads to a doc which is stored in the folder. Each doc has a variety of stuff going on.

Unique to each instance

  • file. The actual path to the file. It is treated as unique and there is a scope dedicated to it. Don't mess with it. It is also how docs are keyed in the object.
  • text. The actual text of the file.
  • blockOff. This tracks whether to take in code blocks as usual. See blocks directive. If 0, code blocks are queued up. If greater than 1, code blocks are ignored.
  • levels. This tracks the level of the heading that is currently being used. See h5/h6 description
  • blocks. Each heading gets its own key in the blocks and the raw code blocks are put here.
  • heading, curname. These are part of the block parsing. curname is the full name while heading excludes minor block names.
  • vars. This is where the variables live. As each code block is compiled, its result gets stored here. But one can also add any bit of var name and text to this.
  • parent. This is the folder that contains this doc.

Inherited from folder

  • commands, modifications affect all
  • directives, modifications affect all
  • scopes, modifications affect all
  • gcd, modifications affect all. Be careful to scope added events to files, etc.
  • plugins, modifications affect all
  • colon
  • join, overwriting will only affect doc
  • log, overwriting will only affect doc
  • subnameTransform, overwriting will only affect doc
  • indicator, overwriting will only affect doc
  • wrapSync, wrapAsync, overwriting will only affect doc
  • augment, this augments the object with the type.
  • cmdworker, this will call the command. needed as with the dot command, it can get tricky. Used in .apply, .mapc, compose.
  • compose, this creates a function from composing multiple commands

Prototyped on Doc. Almost all are internal and are of little to no interest.

  • pipeParsing. This parses the pipes. This may be useful if you want to do something like in the save or define directives. Check them out in the source if you want to see how to use it.
  • blockCompiling. This

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