Introduction

The Scripta compiler translates source text written in a markup language to an Elm representation of Html.

Markup Languages

The languages supported by Scripta are

• L0
• microLaTeX
• XMarkdown

Blocks

The text of these markup languages should be thought of as structured into blocks, the content of which is written in an internal language. For example, in microLaTeX, one might have the text below. There are seven blocks, each of which is separated from its neighbor by an empty line. The first block is a paragraph; its content consists of plain text followed by the TeX macro expression \italic{prime} followed by more plain text.

Let's talk about \italic{prime} numbers.

\begin{theorem}
There are infinitely many primes $p$, and in fact
there are infinitely many primes 

\begin{equation}
p \equiv 1 \ \text{mod}\ 4
\end{equation}

and also

\begin{equation}
p \equiv 1 \ \text{mod}\ 8
\end{equation}

and so on.
\end{theorem}

The first paragraph of the theorem was known to Euclid. 

The body of the theorem block consists of six blocks — the three paragraph blocks Let's talk ..., and also, and and so on. There also the two equation blocks. The blocks in the body of the theorem block constitute the \italic{children} of the block. It is the job of the parser to (1) discover the forest structure, and (2) to parse the content of the blocks.

Note that we can visualize the block structure as an outline, as below.

PARAGRAPH

THEOREM

  PARAGRPH

  EQUATION

  EQUATION

  PARAGRAPH

PARAGRAM

In some languages, e.g. L0 and Markdown, the block structure is literally given by the "outline" structure, that is, by indentation. Below is our example rewritten in L0:

Let's talk about [italic prime] numbers.

| theorem
    There are infinitely many primes $p$, and in fact
    there are infinitely many primes 

    || equation
    p \equiv 1 \ \text{mod}\ 4

    and also

    || equation
    p \equiv 1 \ \text{mod}\ 8

    and so on.

The first paragraph of the theorem was known to Euclid. 

Note that an outline is fully equivalent to a tree:

|-- PARAGRAPH
|-- THEOREM
    |- PARAGRAPH
    |- EQUATION
    |- EQUATION
    |- PARAGRAPH
|- PARAGRAPH

Internal Language

While the surface syntax in L0, microLaTeX and XMarkdown depends on the language, the abstract syntax is the same for all tree. Indeed, text in the internal language always parses to Either String (List Expr), where

type Expr
    = Fun String (List Expr) Meta
    | Text String Meta
    | Verbatim String String Meta

Block Definition

In the case of L0 and XMarkdown, a primitive block is defined by

type alias PrimitiveBlock =
    { indent : Int
    , lineNumber : Int
    , position : Int
    , content : List String
    , name : Maybe String
    , args : List String
    , properties : Dict String String
    , sourceText : String
    , blockType : PrimitiveBlockType
    , error : Maybe { error : String }
    }

In the case of MicroLaTeX, there are two additional fields, level: Int and status: Status.