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FMark Build Status

FSharp markdown implementation with additional functionality.


  • Macros
  • Includes
  • Spreadsheet functionality
  • Table of Contents generation
  • Citations and footnotes

See example.fmark for usage examples.

How to use

FMark Plugin Visual Studio Code


  • Open Preview (ctrl+shift+M)

Open a live preview of the HTML that will be generated by FMark.

  • Create HTML File

Create an HTML file in the same directory as the .fmark file, with .html instead of .fmark.

Vanilla Markdown


  • HTML passthrough
  • Lists
  • Links (relative links within file don't work in VSCode, use Create HTML File and preview that.)
  • Images (images don't work in VSCode, use Create HTML File and preview that.)
  • Headers
  • Styling (bold, italic, bold and italic, strikethrough)
  • Paragraphs
  • Quotes
  • Code blocks
  • Tables

Design decisions


  • A list ends with two endlines, i.e., \r\n\r\n
  • List items are separated by one endline
  • List type is determined by the first item.
    • NUMBER ; DOT will be ordered list
    • - or * will be unordered list
  • If the first item does not start with NUMDER;DOT;Space| "- " | "* ", the list type will be default to unordered list
  • Ordered list start number is determined by the first item
    • The subsequent counting is +1 for each list item
  • Two spaces as one level of indentation.
  • A tab, \t character will be interpreted as four spaces, therefore two levels of indentation.


  • All headers must be preceded by two endlines, with an exception made for the first line in a file.

\n\n# header\n is a header, otherwise unless the header is the first line in a file it won't be processed as a header.


  • When using underscores for styling, there must be a space (or endline on the right) on either side in order for it to be recognised.
  • Asterisks for styling work as usual.


[ ]_em_[ ], [ ]__a strong__[ ], or [ ]_em_$, [ ]__a strong__$


A paragraph is some characters that does not match:

  • CodeBlock
  • Header
  • ContentTable (Table of Contents object)
  • List
  • Quote
  • Table
  • Reference

It terminates with two endlines. Any elements mentioned above cannot exist in a paragraph. Otherwise, they will become normal text, and will not be rendered as expected.


To build fmark, dotnet and fable have to be installed first. To build the javascript as well, yarn or npm are needed.

Using the Build script

# build only javascript
build -b js

# build and test every single module
build -b testall

# build js and cli
build -b all

Markdown extensions


Supported Constructs

These are the supported constructs in the preprocessor.

Supported Syntax Description Tested
Simple Macro {% macro name value %} Sets the Macro name equal to the string value Unit Test
Function Macro {% macro name(arg1; arg2) value %} Sets the Macro name equal to the string value with two parameters. Unit Test
Simple Evaluation {{ macro_name }} Evaluates the macro macro_name and replaces the evaluation with the evaluated body of the macro. Unit Test
Function Evaluation {{ macro_name(arg 1; arg 2) }} Evaluates the macro macro_name with the arguments arg 1 and arg 2 and replaces the evaluation with the evaluated body of the macro. Unit Test
File Include {{ include relative/path/to/file }} Includes and preprocesses a file using a relative or absolute path. The macros declared in that file will then be available in the current file Unit Test
Complex Macro Evaluation {{ x( {{ y( {{z}} ; Hello ) }} ; {{z}} ) }} Nested macro evaulations are supported. This way, default arguments can be created for other macros. Unit Test

Supported Features

These are the features that are currently supported by the preprocessor.

Feature Example Description Tested
Simple whitespace control {% macro x y %} evaluates to y and not y . Removes whitespace and newlines in macros where one wouldn't expect them to be added to the macro body. Unit Test
Shadowing of macros through {% macro x x %} {% macro y(x) {{ x }} %} with {{ y(z) }} will evaluate to z but {{ x }} outside of the macro will always evaluate to x. Macros can be shadowed by arguments of other macros. Unit Test
Nested macros {% macro x {% macro y %} %} Macro y is only defined inside macro x and cannot be seen outside of the scope of x. Unit Test
Shadowing of macros through {% macro x x %} {% macro y {% macro x z %} {{x}} %} y: {{ y }}, x: {{ x }} will evaluate to y: z, x: x Macros can be shadowed by other macros which will be used instead for evaluation. Unit Test
Evaluation of large strings {{ x(This is the first argument; This is the second argument) }} One can pass large strings as arguments to the macros. Unit Test
Escaping of characters inside argument {{ x(arg 1 with a \); arg 2 with a \;) }} One can esape all the special characters inside macros and substitutions Unit Test
Escaping macros \{% macro x y %} This will escape the whole macro and not evaluate it Unit Test
Escaping Subsitutions \{{ x }} will not evaluate the substitution but instead output it literally Unit Test
Outputting unmatched subsituttion {{ x }} -> {{ x }} if not in scope If the subsitution is not matched, it will output it as it got it Unit Test
Nested Evaluations {{ x( {{y}} ) }} Arguments can now be evaluated inside them. Unit Test


To use the preprocessor and the lexer, a string or a list of strings can be used, depending on if there are multiple lines or not. For a single string, the following can be used.

For string, the preprocess and lex functions.

let main =
    let inputString = (* Read the string *)

    |> preprocess
    |> lex

For a list of strings, one can use the preprocessList and lexList functions.

let main =
    let inputStringList = (* Read the string list *)
    |> preprocessList
    |> lexList


In markdown using the preprocessor, one can then write the following:

Text before macro
{% macro Hello(arg1; arg2)
This is text inside the macro, with semicolons;
{% macro local(arg1; arg2)
This is the second macro
Now back in the first macro.
{{ local(arg1; arg2) }}
Outside both macros
Should be printed as not in scope: {{ local(arg1; arg2) }}

{{ Hello(arg1; arg2) }}

which then evaluates to

Text before macro
Outside both macros
Should be printed as not in scope: {{ local(arg1; arg2) }}

This is text inside the macro, with semicolons;
Now back in the first macro.

This is the second macro 

More complicated macros can also be created by writing html in the macros. Due to the html passthrough in the lexer, the html will be copied over literally to the output html.


The lexer supports HTML pass through, which can be used to display raw html in markdown. Using this with macros can give very useful and interesting functions.

Interface to the Parser

The interface to the parser was done using the following Token type, which the parser takes in and can parse.

type Token =
    | CODEBLOCK of string * Language
    | LITERAL of string
    | WHITESPACE of size: int
    | NUMBER of string


Supports escaping of all the special characters defined in Types. This is done by adding a \ in front of the character that should be escaped.

Tokens that match multiple characters can also be escaped by just putting a \ before it. For example, *** can be escaped by writing \***.


It can easily be extended by adding the type of the token to Token above. Then the string has to be linked to the token by adding it as a tuple of type string * Token to a list called charList in the Lexer.

Spreadsheet functionality

Spreadsheet functions will evaluate in-place, if they are incorrectly formatted then Markalc will leave the cell unchanged as if it were normal text inside.

To delineate an expression, start the cell with the = operator, e.g.

Calcs 39 42
=6*5+SUM{4,5} =[1,1]+3



Function Syntax Effect Tested
Modulo a%b a modulo b Property based, all integer inputs.
Power a^b a to the power of b Property based, all integer inputs.
Multiply a*b a times b Property based, all integer inputs.
Division a/b a divided by b Property based, all integer inputs.
Subtraction a-b a minus b Property based, all integer inputs.
Addition a+b a plus b Property based, all integer inputs.
Brackets a+(b-c) Specify order of operation. Unit tested.
Cell References [0,2] Evaluates to contents of cell specified (row 0, col 2) Unit tested
Range Cell Ref [0,0]:[2,0] Evaluates to list of cell references. Unit tested.
Keyword Cell Ref [col=2,row=0] Alternative syntax, order doens't matter. Unit tested
Specify Decimal Places =5.333,2 Comma then a number specifies number of decimal places. Unit tested
Cell reference behaviour
Referenced cell Return
Contains valid expression =... Contents of cell
Does not contain valid expression nan
Is not in table nan
Contains circular reference nan


Supported functions:

Function name Effect Tested
SUM Adds all arguments. Unit tested.
AVG Calculates mean of all arguments. Unit tested.
MIN Returns minimum of all arguments. Unit tested.
MAX Returns maximum of all arguments. Unit tested.

Functions support Range Cell References: [0,0]:[2,0] will evaluate to [0,0],[1,0],[2,0]. This can be used with other arguments, e.g. SUM{[0,0]:[2,0],1,3+2,[0,0]}


Feature Example Workaround
Negative numbers =-a+b Subtract number from zero in brackets e.g. =(0-a)+b
Integer operations =5+2 All calculations done in floating point.
Allow formatting around equation *=5+2* None
String operations e.g. Excel CONCAT None
Assume empty cells are zero Summing over column with empty cells Put =0 in each cell

Table of Contents

Table of Contents can be build anywhere with %%TOC. Relative linking is supported, clicking an item from the contents table will jump to the respective header when viewed in html.

Feature Example Exaplanation
depth %%TOC depth=3 Build a TOC with headers level less than 3
exclude %%TOC excludes=[Appendix;Acknowledgement] Exclude headers with name Appendix and Acknowledgement

Multiple features can be stacked with , like so:

%%TOC depth=3, excludes=[Appendix;Acknowledgement]


FMark supports simple footers and styled references.

  • If multiple citations with the same reference ID is found, the first citation will be used inline.

    • One [^fmark] inline, and two [^fmark], some author. The first will be used.
  • Reference to non-exist citation will result in "[Reference: %refID not found!]" in the HTML generated.

  • The list is sorted, with footnotes in order of their numerical IDs first, References in order of apperance after. Thus the order each explanatory text comes in the fmark file does not matter.

Simple Footers

Simple footers have numerical IDs.

this is inline[^1], and so on.

[^1], this is the text to explain such line.
      this line as well.
But not this line.

The body will show up with a superscripted link:

this is inline1 , and so on.

But not this line.

The footer texts will be collected at the end of the document.

1: this is the text to explain such line. this line as well.

Styled References

Styled references have alphabetic IDs.

Supported rendering styles:

Chicago Harvard IEEE
Book Yes Yes -
Website Yes Yes -

Supported data fields

Field Explanation
type 'Book' or 'Website'
author Author with surname at the end
title Title
year The year it is written
url Address for website
access Date of access for websites, in yyyy-mm-dd format

Pick a style with %%RefStyle, or it will default to Harvard.

%%RefStyle = Harvard

Then follow field1=data1, field2=data2, ... to use references.

Spaces around equal sign are allowed, so f = d, f= d, f =d or f=d all have the same effect.

This is a citation[^Mark]. This is another[^FMark] one.

[^Mark], type= Book, author= Mark Smith, title= Not a real book, year= 2018
[^FMark], type= Website, author= FMark Smith, title= Not a real website, year= 2017 url= access= 2018-3-4

With Harvard, it will look like this:

This is a citation(Smith, 2018). This is another(Smith, 2017) one.

At the end of the document:

Smith, M. (2018) Not a real book.

Smith, F. (2017) Not a real website. Available from: [Accessed 4th March 2018].

if Chicago style is chosen:

This is a citation(Smith 2018). This is another(Smith 2017) one.

At the end of the document:

Mark Smith. 2018. Not a real book.

FMark Smith. 2017. "Not a real website." Accessed March 3, 2018.

Latex maths rendering

Fmark includes support for Latex maths rendering.

Surround an equation written in Latex with $$ in order to use this feature.

Example: $$2+2=4-1=3$$

You can’t perform that action at this time.