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https://github.com/jxxcarlson/L1
toy language demo for a fault-tolerant parser
https://github.com/jxxcarlson/L1
Last synced: about 2 months ago
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toy language demo for a fault-tolerant parser
- Host: GitHub
- URL: https://github.com/jxxcarlson/L1
- Owner: jxxcarlson
- Created: 2021-07-09T11:58:29.000Z (over 3 years ago)
- Default Branch: main
- Last Pushed: 2021-08-05T15:52:33.000Z (over 3 years ago)
- Last Synced: 2024-02-13T10:02:47.646Z (11 months ago)
- Language: Elm
- Size: 615 KB
- Stars: 0
- Watchers: 4
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
- awesome-elm-pltd - L1 - A toy language demo for a fault-tolerant parser. (Languages / Markup Languages)
README
# Fault-Tolerant Parsing
*Note.* To experiment with L1, please go to [l1-lab.lamdera.app](https://l1-lab.lamdera.app)
The goal of this article is to explain how one can implement a fault-tolerant parser for a simple language, which we will call **L1**. Here are a few sentences in L1:
```
This [i is [b not] a very good] test.
```
It would be rendered as "This _is_ _**not** a very good_ test." The language consists
of ordinary text and _elements_, which have the form
```
[name body]
```
where the body is itself an element, e.g., plain text, an element, or
a list of elements, e.g.,
- [link NYT https://nytimes.com]
- [link "New York Times" https://nytimes.com]
- [fontRGB 255 0 255 [i This text is in [b magenta]]]
- [image caption:Songbird width:400 placement:left https://birds/warbler.png]
- [math a^2 + b^2 = c^2]
The syntax is thus somewhat like Lisp, where
an elements like `[i foo]` means "render 'foo' in italic.
A conventional parser reads its input and attempts to convert it to an abstract syntax tree — a data structure that expresses an understanding of the underlying grammar. When such a parser encounters an error, it typically
bails out with a more or less comprehensible error message. Such behavior
is not suited for interactive language editors, where the text will pass
in and out of an error state as the user types away. A _fault-tolerant_ parser should in all cases return an abstract syntax tree that makes sense to the greatest degree possible.
[Error recovery with parser combinators](https://eyalkalderon.com/blog/nom-error-recovery/)