litrepl 3.13.0
Litrepl evaluates code from LaTeX/Markdown verbatim sections.
Requires Python: >=3.6


<!--
vim: tw=80
--!>
Changelog
=========

Version 3.13.0
--------------

1. **Python**
   - Improved backward compatibility by fixing issues related to spurious
     newlines on empty inputs.
   - Accept `codeai` code section for AI interpreters, in addition to `ai`.
   - Introduced a new command `print-auxdir`.

2. **Environment**
   - Added support for generating coverage reports with updates to the Makefile.
   - Added dependency on coverage-badge, enhancing reporting capabilities.
   - Modified settings to ignore empty `LITREPL_` environment variables.

3. **Vim**
   - Enhanced the indentation feature in Litrepl to preserve empty lines.
   - Updated the status command to print the auxiliary directory and fixed an
     unwanted exception.

Version 3.12.0
--------------

1. **Python**
   - Fix the hashing algorithm to exclude the unstable `hash()` output from
     digests thus fixed an issue with handling a `None` suffix in digests,
     improving the stability and accuracy of digest computations.
   - Section addressing has been adjusted to start from 1 instead of 0 for
     readability.
   - Made `eval-sections` the default command, reflecting a focus on ease of use
     and user interaction.

2. **Environment**
   - Underscores have been removed from auxiliary directory file names.
   - Add a link to the arXiv [paper](https://arxiv.org/abs/2501.10738).

3. **Vim**
   - Added new options for ignoring specific LaTeX sections with the `lignore`
     feature, enhancing customization for LaTeX users.
   - Updated the Vim async tag pattern `BG` -> `LR`.


Version 3.11.0
--------------

1. **Python**
   - The interpreters have been refactored into their own submodule, improving
     code organization.
   - Added preliminary support for
     [shell](./python/litrepl/interpreters/shell.py) interpreters, allowing the
     system to handle shell commands.
   - Introduced new commands: `print-grammar` to output the grammar and
     `print-regexp` for regular expression management.
   - Introduced adjustable code section labels, removing the default `lcode`
     sections support.
   - Improved debugging and configuration support in IPython by ensuring
     expanded paths and correct handling of the DEBUG setting.
   - Support for automatic file type detection with `--filetype=auto` has been
     implemented.
   - The support for `--irreproducible-exitcode` argument was added

2. **Vim**
   - Fixed cursor handling issues in `LEvalMon`, improving text navigation and
     evaluation feedback within Vim.
   - Improve error reporting performed by the `LOpenErr` command.

Version 3.10.1
--------------

Minor environment changes

Version 3.10.0
--------------

1. **Python**
   - Code refactoring for better code management and efficiency: moved main
     logic in `litrepl` from `python/bin/litrepl` to a new file
     [python/litrepl/main.py](./python/litrepl/main.py).
   - Improved handling of subprocess management for the Python and AI
     interpreters, ensuring proper cleanup and output management. Additionally,
     calls to `os.system` were mostly replaced with native Python calls.
   - Added robust error handling and message retrieval for the interpreter
     interface, providing clearer errors when the interpreter fails.

2. **Vim**
   - Introduced the default environment variable check for `LITREPL_WORKDIR`,
     `LITREPL_PYTHON_AUXDIR`, `LITREPL_AI_AUXDIR` etc. environment variables.
   - Updated Vim functions to consider both buffer and global settings,
     improving flexibility in command generation (`LitReplGet` helper function).
   - Updated commands related to AI tasks like `:LAIStyle`, `:LAIFile`, and
     `:LAICode` to handle rephrasing and AI interaction more efficiently.
   - Adjusted internal Vim functions to handle text width settings and cursor
     positionings.

3. **Environment**
   - Replaced `test.sh` with [runtests.sh](./sh/runtests.sh) in the build and test
     process for enhanced test execution flow.
   - Allowed more environment configuration by introducing more settings that
     default from environment variables, streamlining setup customization.
   - Updated Nix build script ([default.nix](./default.nix)) to reflect changes
     in the test script location and hash updates for source verification.
   - Added this changelog and the AI-powered changelog helper script
     [diffchanges.sh](./sh/diffchanges.sh).

Version 3.9.0
-------------

1. **Python**
   - Added assertions to ensure a successful attachment to the interpreter,
     enhancing error handling robustness.

2. **Vim**
   - Enhanced [vim/plugin/litrepl.vim](./vim/plugin/litrepl.vim) by preserving
     caret positions and restructuring comments for function alignment.
   - Significant expansions in
     [vim/plugin/litrepl_extras.vim](./vim/plugin/litrepl_extras.vim) with
     multiple new functions for region handling, AI task management, and
     interaction across different scopes, substantially improving user
     experience with AI functionalities in Vim. Several new commands such as
     `LAITell`, `LAICont`, `LAIStyle`, `LAIFile`, and `LAICode` are introduced
     to support a wide range of code and AI-related tasks.

3. **Environment**
   - Added a new markdown file `./doc/screencast.md` with examples for
     evaluating Python code in Vim, offering insights into the screencast
     documentation process.
   - Adjusted `screencast.sh` to be executable and made improvements to
     accommodate a target file parameter.
   - Introduced a new test function `test_vim_ai_query` in `test.sh`,
     facilitating new test coverage for AI query functionality.


<div align="center">
<h1>
⌨️ LitRepl ⌨️
</h1>

[Changelog](./CHANGELOG.md) | [Installation](#-installation) | [Usage](#basic-execution) | [Gallery](#-gallery)

[![](./img/coverage.svg)](#-coverage-report)
</div>

**Litrepl** is a command-line processor for *Markdown* or *LaTeX* documents with
**literate programming** code sections. Instructed by its arguments, it
evaluates and updates sections via background interpreters. Interpreters can
stay active for a **read-eval-paste-loop** style. The repository includes a Vim
plugin to demonstrate editor integration.

<div align="center">

![Peek 2024-07-18 20-50-2](https://github.com/user-attachments/assets/8e2b2c8c-3412-4bf6-b75d-d5bd1adaf7ea)

</div>


_Notes:_
* _[literate programming](https://en.wikipedia.org/wiki/Literate_programming)_
* _[read-eval-print-loop coding](https://en.wikipedia.org/wiki/Read%E2%80%93eval%E2%80%93print_loop)_


<table border="0">
  <tr>
    <td>
      <a href="https://arxiv.org/abs/2501.10738">
        <img src="img/adobe_pdf.png" alt="PDF Icon">
      </a>
    </td>
    <td>
      Preprint: <i>(2025, Sergei Mironov)</i>
      <ins>Litrepl: Literate Paper Processor Promoting Transparency More Than Reproducibility</ins>
      <a href="https://arxiv.org/abs/2501.10738">arXiv:2501.10738</a>
    </td>
  </tr>
</table>

🔥 Features
-----------

* **Document formats** <br/>
  Markdown _(Example [[MD]](./doc/example.md))_ **|**
  [LaTeX](https://www.latex-project.org/)
  _(Examples [[TEX]](./doc/example.tex)[[PDF]](./doc/example.pdf))_
* **Interpreters** <br/>
  [Sh](https://en.wikipedia.org/wiki/Bourne_shell) **|**
  [Bash](https://www.gnu.org/software/bash/) **|**
  [Python](https://www.python.org/) **|**
  [IPython](https://ipython.org/) **|**
  [Aicli](https://github.com/sergei-mironov/aicli)
* **Editor integration** <br/>
  [Vim](https://www.vim.org/scripts/script.php?script_id=6117) _(plugin source included)_

✅ Requirements
---------------

* **POSIX-compatible OS**, typically a Linux. The tool relies on POSIX
  operations, notably pipes, and depends on certain Shell commands.
* **lark-parser** and **psutil** Python packages.
* **[Socat](http://www.dest-unreach.org/socat/)** (Optional) Needed for
  `litrepl repl` and Vim's `LTerm` commands to work.

📚 Contents
-----------

<!-- vim-markdown-toc GFM -->

* [⚙️ Installation](#-installation)
* [🚀 Usage](#-usage)
    * [General Concepts](#general-concepts)
        * [Basic Execution](#basic-execution)
        * [Selecting Sections for Execution](#selecting-sections-for-execution)
        * [Managing Interpreter Sessions](#managing-interpreter-sessions)
        * [Asynchronous Processing](#asynchronous-processing)
        * [Attaching Interpreter Sessions](#attaching-interpreter-sessions)
        * [Experimental AI Features](#experimental-ai-features)
    * [Application Scenarios](#application-scenarios)
        * [Command Line, Foreground Evaluation](#command-line-foreground-evaluation)
        * [Command Line, Detecting Python Exceptions](#command-line-detecting-python-exceptions)
        * [GNU Make, Evaluating Code Sections in Project Documentation](#gnu-make-evaluating-code-sections-in-project-documentation)
        * [Vim, Setting Up Keybindings](#vim-setting-up-keybindings)
        * [Vim, Inserting New Sections](#vim-inserting-new-sections)
        * [Vim, Running the Initial Section After Interpreter Restart](#vim-running-the-initial-section-after-interpreter-restart)
        * [Vim, Evaluating Selected Text](#vim-evaluating-selected-text)
        * [Vim, Calling for AI on a visual selection](#vim-calling-for-ai-on-a-visual-selection)
    * [In-Depth Reference](#in-depth-reference)
        * [Vim Commands and Command-Line Attributes](#vim-commands-and-command-line-attributes)
        * [Command Line Arguments and Vim Variables](#command-line-arguments-and-vim-variables)
        * [Command Line Arguments Summary](#command-line-arguments-summary)
* [🏗️ Development Guidelines](#-development-guidelines)
    * [Building Targets](#building-targets)
    * [Development Environments and Setup](#development-environments-and-setup)
    * [Tools for Screencast Recording](#tools-for-screencast-recording)
    * [Common Development Scenarios](#common-development-scenarios)
* [🎥 Gallery](#-gallery)
* [🖼️ Coverage report](#-coverage-report)
* [💡 Technical Insights](#-technical-insights)
* [🚫 Known Limitations](#-known-limitations)
* [Related Tools and Projects](#related-tools-and-projects)
* [Considerations for Third-Party Tools](#considerations-for-third-party-tools)

<!-- vim-markdown-toc -->

<a name="-installation"></a>

⚙️ Installation
--------------

This repository hosts the Litrepl tool, a standalone command-line application
and an interface plugin for the Vim editor. The author's preferred installation
method is using Nix, but if you choose not to use it, you'll need to install one
or both components separately. Below, we outline several common installation
methods.

<details open><summary><b>Release versions, from Pypi and Vim.org</b></summary><p>

1. `pip install litrepl`
2. Download the `litrepl.vim` from the vim.org
   [script page](https://www.vim.org/scripts/script.php?script_id=6117) and put it into
   your `~/.vim/plugin` folder.

</p></details>

<details><summary><b>Latest versions, from Git, using Pip and Vim-Plug</b></summary><p>

1. Install the `litrepl` Python package with pip:
   ``` sh
   $ pip install --user git+https://github.com/sergei-mironov/litrepl
   $ litrepl --version
   ```
2. Install the Vim plugin by adding the following line between the
   `plug#begin` and `plug#end` lines of your `.vimrc` file:
   ```vim
   Plug 'https://github.com/sergei-mironov/litrepl' , { 'rtp': 'vim' }
   ```
   Note: `rtp` sets the custom vim-plugin source directory of the plugin.

</p></details>

<details><summary><b>Latest versions, from source, using Nix</b></summary><p>

The repository offers a suite of Nix expressions designed to optimize
installation and development processes on systems that support Nix. Consistent
with standard practices in Nix projects, the [flake.nix](./flake.nix) file
defines the source dependencies, while the [default.nix](./default.nix) file
identifies the build targets.

For testing, the `vim-demo` expression is a practical choice. It includes a
pre-configured Vim setup with several related plugins, including Litrepl. To
build this target, use the command `nix build '.#vim-demo'`. Once the build is
complete, you can run the editor with `./result/bin/vim-demo`.

To add the Litrepl tool to your system profile, first include the Litrepl flake
in your flake inputs. Then, add `litrepl-release` to
`environment.systemPackages` or to your custom environment.

To include the Litrepl Vim plugin, add `vim-litrepl-release` to the `vimPlugins`
list within your `vim_configurable` expression.

Regardless of the approach, Nix will manage all necessary dependencies
automatically.

Nix are used to open the development shell, see the [Development](#development)
section.

</p></details>

<details><summary><b>Latest versions, from source, using Pip</b></summary><p>

The Litrepl application might be installed with `pip install .` run from the
project root folder. The Vim plugin part requires hand-copying
`./vim/plugin/litrepl.vim` and `./vim/plugin/litrepl_extras.vim` to the `~/.vim`
config folder.

</p></details>

The Nix-powered installation methods install the Socat tool automatically. For
other installation methods, use your system pacakge manager to install it. For
example, Ubuntu users might run `sudo apt-get install socat`.

The Python interpreter is usually installed by default, along with the `pip`
installer. To install `ipython`, you can use `pip install ipython`. For the
[aicli](https://github.com/sergei-mironov/aicli) interpreter, you can run `pip
install sm_aicli`, or refer to the project page for additional installation
methods.

🚀 Usage
--------

### General Concepts

The Litrepl tool identifies code and result sections within a text document. It
processes the code by sending it to the appropriate interpreters and populates
the result sections with their responses. The interpreters remain active in the
background, ready to handle new inputs.

Litrepl supports subsets of **Markdown** and **LaTeX** formatting in order to
recognize the sections. Some aspects of the recognized grammars, such as section
labels, could be configured.

#### Basic Execution

Litrepl searches for verbatim code sections followed by zero or more result
sections. In Markdown documents, the Python code is any triple-quoted section
with a pre-configured label such as `python`. The result is any triple-quoted
`result` section.  In LaTeX documents, sections are marked with
`\begin{...}\end{...}` environments correspondingly.

The primary command for evaluating formatted documents is `litrepl
eval-sections`. Consider a [hello.md](./doc/hello.md) document:

<!--
``` python
print("~~~~ markdown")
!cat doc/hello.md
print("~~~~")
```
-->

<!-- result -->
~~~~ markdown
``` python
print('Hello Markdown!')
```
``` result
```
~~~~
<!-- noresult -->

You pass it to Litrepl using:

~~~~ shell
$ cat hello.md | litrepl eval-sections > result.md
~~~~

The `result.md` will have all sections filled in correctly.
<!--
``` python
print("~~~~ markdown")
!cat doc/hello.md | litrepl --foreground eval-sections
print("~~~~")
```
-->

<!-- result -->
~~~~ markdown
``` python
print('Hello Markdown!')
```
``` result
Hello Markdown!
```
~~~~
<!-- noresult -->

* For additional details on Markdown formatting, refer to [Formatting Markdown
  documents](./doc/formatting.md#markdown)

Similarly, in a LaTeX document, we format code and result sections as follows:

~~~~ tex
\begin{python}
print('Hello LaTeX!')
\end{python}

\begin{result}
Hello LaTeX!
\end{result}
~~~~

- LaTeX documents require a preamble introducing python/result environments to
  the TeX processor. For more information, see [Formatting LaTeX
  documents](./doc/formatting.md#latex).

By default, Litrepl tried to guess the format of the input document. Use the
`--filetype=(latex|markdown)` option to set the format explicitly:

``` sh
$ cat doc.md | litrepl --filetype=markdown eval-sections
$ cat doc.tex | litrepl --filetype=latex eval-sections
```

* The main Vim command for code section evaluation is `:LEval`. By default, it
  executes the section at the cursor. To execute all sections in a document, use
  `:LEval all`.

#### Selecting Sections for Execution

By default, `litrepl eval-sections` evaluates all sections in a document. To
evaluate only specific sections, the range argument should be specified. The
overall syntax is `litrepl eval-sections [RANGE]`, where `RANGE` can be:

* `N`: Represents a specific code section to evaluate, with the following
  possible formats:
  - A number starting from `0`.
  - `$` symbol, indicating the last section.
  - `L:C`, referring to the line and column position. Litrepl calculates the
    section number based on this position.
* `N..N`: Represents a range of sections, determined using the rules mentioned
  above.

Some examples:

``` sh
$ litrepl eval-sections '0'       # First section in a document
$ litrepl eval-sections '3..$'    # Sections from fourth section (zero based) to the last one
$ litrepl eval-sections '34:1..$' # Sections starting from line 34 column 1
```

* The Vim command `:LEval` accepts similar syntax and also recognizes specific
  keywords `all`, `above`, and `below`. These keywords allow you to evaluate all
  sections, only those above the cursor, or just the ones below the cursor,
  respectively.

#### Managing Interpreter Sessions

Each interpreter session uses an auxiliary directory where Litrepl stores
filesystem pipes and other runtime data.

By default, the auxiliary directory path is derived from the working directory
name (for Vim, this defaults to the directory of the current file).

This behavior can be configured by:
* Setting the working directory with `LITREPL_WORKDIR` environment
  variable or `--workdir=DIR` command-line argument (this may also affect the
  current directory of the interpreters), or
* Explicitly setting the auxiliary directory with `LITREPL_<CLASS>_AUXDIR`
  environment variable or `--<class>-auxdir=DIR` command-line argument, where
  `<class>` stands for either `python`, `ai` or `sh`.


The commands `litrepl start CLASS`, `litrepl stop [CLASS]`, and `litrepl restart
[CLASS]` are used to manage interpreter sessions. They accept the interpreter
type to operate on or (for some commands) the keyword `all` to apply the command
to all interpreters. Add the `--<class>-interpteter=CMDLINE` to adjust the
command line to run, but be careful - Litrepl adds more arguments to configure
prompts and verbosity to some interpreters, notably to the pythons.

``` sh
$ litrepl --python-interpreter=ipython start python
$ litrepl --sh-interpreter=/opt/bin/mybash start sh
$ litrepl restart all
$ litrepl stop
```

* The equivalent Vim commands are `:LStart CLASS`, `:LStop [CLASS]`, and
  `:LRestart [CLASS]`. For the corresponding Vim configuration variables, see
  the reference section below.


The `litrepl status [CLASS]` command queries the information about the currently
running interpreters. The command reveals the process PID and the command-line
arguments. For stopped interpreters, the last exit codes are also listed.
Specifying `CLASS` prints the status for this class of interpreters only.

``` sh
$ litrepl status
# Format:
# CLASS  PID      EXITCODE  CMD
python   3900919  -         python3 -m IPython --config=/tmp/litrepl_1000_a2732d/python/litrepl_ipython_config.py --colors=NoColor -i
ai       3904696  -         aicli --readline-prompt=
```

* The corresponding Vim command is `:LStatus`. No `CLASS` argument is currently
  supported.

#### Asynchronous Processing

Litrepl can generate an output document before the interpreter has finished
processing. If the evaluation takes longer than a timeout, Litrepl leaves a
marker, enabling it to continue from where it was stopped during future runs.
The `--timeout=SEC[,SEC]` option allows you to set timeouts. The first number
specifies the initial execution timeout in seconds, while the optional second
number sets the timeout for subsequent attempts. By default, both timeouts are
set to infinity.

For instance, executing `litrepl --timeout=3.5 eval-sections` on the
corresponding program yields:

<!--lignore-->
~~~~ markdown
``` python
from tqdm import tqdm
from time import sleep
for i in tqdm(range(10)):
  sleep(1)
```

``` result
 30%|███       | 3/10 [00:03<00:07,  1.00s/it]
[BG:/tmp/nix-shell.vijcH0/litrepl_1000_a2732d/python/litrepl_eval_5503542553591491252.txt]
```
~~~~
<!--lnoignore-->

Upon re-executing the document, Litrepl resumes processing from the marker. Once
evaluation concludes, it removes the marker from the output section.

The command `litrepl interrupt` sends an interrupt signal to the interpreter,
prompting it to return control sooner (with an exception).

* The equivalent Vim commands are `:LEvalAsync` (defaulting to a 0.5-second
  timeout) and `:LInterrupt`.
* The Vim plugin also provides the `:LEvalMon` command, which facilitates
  continuous code evaluation with no delay. Interrupting this with Ctrl+C will
  make Litrepl return control to the editor, leaving the evaluation ongoing in
  the background.


#### Attaching Interpreter Sessions

The command `litrepl repl [CLASS]` where `CLASS` specifies interpreter class:
`python` (the default) `ai` or `sh`, attaches to interpreter sessions.  For this
command to work, [socat](https://linux.die.net/man/1/socat) tool needs to be
installed on your system. Litrepl blocks the pipes for the time of interaction
so no evaluation is possible while the repl session is active.  For Python and
Shell interpreters, the command prompt is disabled which is a current technical
limitation. Use `Ctrl+D` to safely detach the session. For example:

``` sh
$ litrepl repl python
Opening the interpreter terminal (NO PROMPTS, USE `Ctrl+D` TO DETACH)
W = 'Hello from repl'
^D
$
```

Use `litrepl eval-code [CLASS]` to direct code straight to the interpreter,
bypassing any section formatting steps. In contrast to the `repl` command,
`eval-code` mode features prompt detection, allowing the tool to display the
interpreter's response and detach while keeping the session open.

For example, after manually defining the `W` variable in the example above, it
can be queried as in a typical IPython session.

``` sh
$ echo 'W' | litrepl eval-code
'Hello from repl'
```

The `eval-code` command can be utilized for batch processing and managing
sessions, in a manner similar to how the `expect` tool is used.

* The equivalent Vim commands are `:LRepl [CLASS]` or `:LTerm [CLASS]`. Both
  commands open Vim terminal window.

#### Experimental AI Features

Litrepl experimentally supports [Aicli](https://github.com/sergei-mironov/aicli)
terminal allowing users to query external language models. In order to try it,
install the interpreter and use `ai` as the name for code sections. For
low-speed models it might be convenient to use `:LEvalMon` command to monitor
the text generation in real time.

<!--lignore-->
~~~~ markdown
``` ai
/model gpt4all:"./_models/Meta-Llama-3-8B-Instruct.Q4_0.gguf"
Hi chat! What is your name?
```

``` result
I'm LLaMA, a large language model trained by Meta AI. I'm here to help answer
any questions you might have and provide information on a wide range of topics.
How can I assist you today?
```
~~~~
<!--lnoignore-->

All Aicli `/`-commands like the `/model` command above are passed as-is to the
interpreter. The `/ask` command is added automatically at the of each section,
so make sure that `ai` secions have self-contained questions.

As a pre-processing step, Litrepl can paste text from other sections of the
document in place of special reference markers. The markers have the following
format:

* `>>RX<<`, where `X` is a number - references a section number `X` (starting
  from zero).
* `^^RX^^`, where `X` is a number - references the section `X` times above the
  current one.
* `vvRXvv`, where `X` is a number - references the section `X` times below the
  current one.

<!--lignore-->
~~~~ markdown
``` ai
AI, what do you think the following text means?

^^R1^^
```

``` result
Another interesting piece of text!
This is an example of a chatbot introduction or "hello message." It appears to
be written in a friendly, approachable tone, with the goal of establishing a
connection with users.
```
~~~~
<!--lnoignore-->


### Application Scenarios

#### Command Line, Foreground Evaluation

When performing batch processing of documents, it might be necessary to initiate
a new interpreter session solely for the evaluation's duration rather than
re-using the currently running session. The `--foreground` option can be used to
activate this mode.

<!--lignore-->
~~~~ shell
$ cat document.md.in | litrepl --foreground eval-sections > document.md
~~~~
<!--lnoignore-->

#### Command Line, Detecting Python Exceptions

Another frequently requested feature is the ability to report unhandled
exceptions. Litrepl can be configured to return a non-zero exit code in such
scenarios.

<!--lignore-->
~~~~ shell
$ cat document.md
``` python
raise Exception("D'oh!")
```
$ cat document.md | litrepl --foreground --exception-exit=200 eval-sections
$ echo $?
200
~~~~
<!--lnoignore-->

In this example, the `--foreground` option instructs Litrepl to start a new
interpreter session, stopping it upon completion. The `--exception-exit=200`
option specifies the exit code to be returned in the event of unhandled
exceptions.


#### GNU Make, Evaluating Code Sections in Project Documentation

A typical Makefile recipe for updating documentation is structured as follows:

``` Makefile
SRC = $(shell find -name '*\.py')

.stamp_readme: $(SRC) Makefile
	cp README.md _README.md.in
	cat _README.md.in | \
		litrepl --foreground --exception-exit=100 \
                --python-interpreter=ipython \
                --sh-interpreter=- \
		eval-sections >README.md
	touch $@

.PHONY: readme
readme: .stamp_readme
```

Here, `$(SRC)` is expected to include the filenames of dependencies. With this
recipe, we can run `make readme` to evaluate the python sections. By passing `-`
wealso tell Litrepl to ignore shell sections.


#### Vim, Setting Up Keybindings

The `litrepl.vim` plugin does not define any keybindings, but users could do it
by themselves, for example:

``` vim
nnoremap <F5> :LEval<CR>
nnoremap <F6> :LEvalAsync<CR>
```

#### Vim, Inserting New Sections

The `litrepl.vim` plugin doesn't include tools for creating section formatting,
however they can be added easily if required. Below, we demonstrate how to
define the `:C` command inserting new `python` sections.

<!--lignore-->
```` vim
command! -buffer -nargs=0 C normal 0i``` python<CR>```<CR><CR>``` result<CR>```<Esc>4k
````
<!--lnoignore-->
<!---``` <- to make TokOpen() happy -->

#### Vim, Running the Initial Section After Interpreter Restart

Below we demonstrate how to define the `:LR` command for running first section
after the restart.

``` vim
command! -nargs=0 LR LRestart | LEval 0
```

#### Vim, Evaluating Selected Text

Litrepl vim plugin defines `LitReplEvalSelection` function which runs the
selection as a virtual code section. The section type is passed as the function
argument.  For example, calling `LitReplEvalSelection('ai')` will execute the
selection as if it is an `ai` code section. The execution result is pasted right
after the selection as a plain text. `LitReplEvalSelection('python')` would pipe
the selection through the current Python interpreter.

To use the feature, define a suitable key binding (`Ctrl+K` in this example),

<!--lignore-->
``` vim
vnoremap <C-k> :call LitReplEvalSelection('ai')<CR>
```
<!--lnoignore-->

Now write a question to the AI in any document, select it and hit Ctrl+K.

~~~~
Hi model. What is the capital of New Zealand?
~~~~

Upon the keypress, Litrepl pipes the selection through the AI interpreter - the
`aicli` at the time of this writing - and paste the response right after the
last line of the original selection.

~~~~
Hi model. What is the capital of New Zealand?
The capital of New Zealand is Wellington.
~~~~

Internally, the plugin just uses `eval-code` Litrepl command.


#### Vim, Calling for AI on a visual selection

The repository includes [litrepl_extras.vim](./vim/plugin/litrepl_extras.vim), which
defines extra tools for interacting with AI. These tools are based on the single
low-level `LitReplAIQuery()` function.

The function enables the creation of an AI chat query possibly incorporating the
current file and any selected text. The AI model's response then returned
alongside with the Litrepl error code.

Based on this function, the following two middle-level functions are defined:
- `LitReplTaskNew(scope, prompt)`
- `LitReplTaskContinue(scope, prompt)`

Both functions take the prompt, produce the AI model response and decide where
to insert it. However, the key difference is that the first function determines
the target location based on user input (like cursor position or selection),
while the second function re-applies the previously used position, allowing
users to make changes easilly.

Finally, a number of high-level commands have been established. Each of these
commands receives an input string that directs the model on what action to take.
The user input can contain `/S` or `/F` tokens, which are replaced with the
values of the visual selection and the current file, respectively.


| Command    | Description                    | Incorporates           | Updates            |
|------------|--------------------------------|------------------------|--------------------|
| `LAI`      | Passes the prompt as-is        | Input, Selection       | Cursor, Selection  |
| `LAICont`  | Passes the prompt as-is        | Input, Selection       | Last               |
| `LAIStyle` | Asks to improve language style | Input, Selection       | Selection          |
| `LAICode`  | Asks to modify a code snippet  | Input, Selection       | Cursor, Selection  |
| `LAITell`  | Asks to describe a code snippet| Input, Selection       | Terminal*          |
| `LAIFile`  | Asks to change a whole file    | Input, Selection, File | File               |

* `LAITell` shows the response in the AI terminal instead of inserting it into
  the document.

As with the selection evaluation mode, the `aicli` interpreter stays
active in the background, maintaining the log of the conversation.

Direct interaction with the interpreter functions as expected. The `LTerm ai`
command opens the Vim terminal as usual, enabling communication with a model
through `aicli` text commands.


### In-Depth Reference

#### Vim Commands and Command-Line Attributes

| Vim <img width=200/> | Command line <img width=200/>    | Description                 |
|----------------------|----------------------------------|-----------------------------|
| `:LStart [T]`        | `litrepl start [T]`              | Start the background interpreter |
| `:LStop [T]`         | `litrepl stop [T]`               | Stop the background interpreter |
| `:LRestart [T]`      | `litrepl restart [T]`            | Restart the background interpreter |
| `:LStatus [T]`       | `litrepl status [T] <F`          | Print the background interpreter status |
| `:LEval [N]`         | `lirtepl eval-sections L:C <F`   | Evaluate the section under the cursor synchronously |
| `:LEval above`       | `lirtepl eval-sections '0..N' <F`| Evaluate sections above and under the cursor synchronously |
| `:LEval below`       | `lirtepl eval-sections 'N..$' <F`| Evaluate sections below and under the cursor synchronously |
| `:LEval all`         | `lirtepl eval-sections <F`       | Evaluate all code sections in a document |
| `:LEvalAsync N`      | `lirtepl --timeout=0.5,0 eval-sections N <F` | Start or continue asynchronous evaluation of the section under the cursor |
| `:LInterrupt N`      | `lirtepl interrupt N <F`         | Send SIGINT to the interpreter evaluating the section under the cursor and update |
| `:LEvalMon N`        | `while .. do .. done`            | Start or continue monitoring asynchronous code evaluation |
| N/A                  | `lirtepl eval-code <P`           | Evaluate the given code verbatim |
| `:LTerm [T]`         | `lirtepl repl [T]`               | Connect to the interpreter using GNU socat |
| `:LOpenErr`          | `litrepl ...  2>F`               | View errors |
| `:LVersion`          | `litrepl --version`              | Show version |

Where

* `T` Type of the interpreter: `python`, `ai` or `sh` (some commands also accept `all`)
* `F` Path to a Markdown or LaTeX file
* `P` Path to a Python script
* `N` Number of code section to evaluate, starting from 0.
* `L:C` denotes line:column of the cursor.

#### Command Line Arguments and Vim Variables

| Vim setting  <img width=200/>   | CLI argument  <img width=200/> | Description                       |
|---------------------------------|--------------------------------|-----------------------------------|
| `set filetype`                  | `--filetype=T`                 | Input file type: `latex`\|`markdown` |
| `let g:litrepl_python_interpreter=B` | `--python-interpreter=B`  | The Python interpreter to use |
| `let g:litrepl_ai_interpreter=B`     | `--ai-interpreter=B`      | The AI interpreter to use |
| `let g:litrepl_sh_interpreter=B`     | `--sh-interpreter=B`      | The shell interpreter to use |
| `let g:litrepl_python_auxdir=D` | `--python-auxdir=D`            | The auxiliary files directory used by Python interpreter |
| `let g:litrepl_ai_auxdir=D`     | `--ai-auxdir=D`                | The auxiliary files directory used by AI interpreter |
| `let g:litrepl_sh_auxdir=D`     | `--sh-auxdir=D`                | The auxiliary files directory used by a shell interpreter |
| `let g:litrepl_workdir=D`       | `--workdir=D`                  | The auxiliary files directory used by AI interpreter |
| `let g:litrepl_debug=0/1`       | `--debug=0/1`                  | Print debug messages to the stderr |
| `let g:litrepl_timeout=FLOAT`   | `--timeout=FLOAT`              | Timeout to wait for the new executions, in seconds, defaults to inf |

* `T` Type of the document: `tex` or `markdown` (the default).
* `B` Interpreter command to use, `-` or `auto` (the default). `-` value
  disabled this type of interpreters; `auto` asks litrep to guess the best
  available interpreter.
* `D` Filesystem directory
* `FLOAT` Should be formatted as `1` or `1.1` or `inf`. Note: command line
  argument also accepts a pair of timeouts.

#### Command Line Arguments Summary

<!--
``` python
!./python/bin/litrepl --help
```
-->

``` result
usage: litrepl [-h] [-v] [--filetype STR] [--python-markers STR[,STR]]
               [--ai-markers STR[,STR]] [--sh-markers STR[,STR]]
               [--python-interpreter EXE] [--ai-interpreter EXE]
               [--sh-interpreter EXE] [--python-auxdir DIR] [--ai-auxdir DIR]
               [--sh-auxdir DIR] [--timeout F[,F]] [--propagate-sigint]
               [-d INT] [--verbose] [-C DIR] [--pending-exitcode INT]
               [--irreproducible-exitcode INT] [--exception-exitcode INT]
               [--foreground] [--map-cursor LINE:COL:FILE]
               [--result-textwidth NUM]

{start,stop,restart,status,parse,parse-print,eval-sections,eval-code,repl,interrupt,print-regexp,print-grammar,print-auxdir}
               ...

positional arguments:

{start,stop,restart,status,parse,parse-print,eval-sections,eval-code,repl,interrupt,print-regexp,print-grammar,print-auxdir}
                              Commands to execute
    start                     Start the background interpreter.
    stop                      Stop the background interpreters.
    restart                   Restart the background interpreters.
    status                    Print background interpreter's status.
    parse                     Parse the input file without futher processing
                              (diagnostics).
    parse-print               Parse and print the input file back
                              (diagnostics).
    eval-sections             Parse stdin, evaluate the specified sections (by
                              default - all available sections), print the
                              resulting file to stdout.
    eval-code                 Evaluate the code snippet.
    repl                      Connect to the background terminal using GNU
                              socat.
    interrupt                 Send SIGINT to the background interpreter.
    print-regexp              Print regexp matching start of code sections for
                              the given file type.
    print-grammar             Print the resulting grammar for the given
                              filetype.
    print-auxdir              Print the auxdir for the given interpreter type.

options:
  -h, --help                  show this help message and exit
  -v, --version               Print version.
  --filetype STR              Specify the type of input formatting
                              (markdown|[la]tex|auto).
  --python-markers STR[,STR]  TODO
  --ai-markers STR[,STR]      TODO
  --sh-markers STR[,STR]      TODO
  --python-interpreter EXE    Python interpreter command line, or `auto`.
                              Defaults to the LITREPL_PYTHON_INTERPRETER
                              environment variable if set, otherwise "auto".
                              Litrepl determines "python" or "ipython" type
                              according to the value.
  --ai-interpreter EXE        `aicli` interpreter command line or `auto`.
                              Defaults to the LITREPL_AI_INTERPRETER
                              environment variable if set, otherwise "auto".
  --sh-interpreter EXE        Shell interpreter command line or `auto`.
                              Defaults to the LITREPL_SH_INTERPRETER
                              environment variable if set, otherwise "auto".
  --python-auxdir DIR         This directory stores Python interpreter pipes.
                              It defaults to LITREPL_PYTHON_AUXDIR if set;
                              otherwise, it's created in the system's
                              temporary directory, named after the current
                              working directory.
  --ai-auxdir DIR             This directory stores AI interpreter pipes. It
                              defaults to LITREPL_AI_AUXDIR if set; otherwise,
                              it's created in the system's temporary
                              directory, named after the current working
                              directory.
  --sh-auxdir DIR             This directory stores AI interpreter pipes. It
                              defaults to LITREPL_SH_AUXDIR if set; otherwise,
                              it's created in the system's temporary
                              directory, named after the current working
                              directory.
  --timeout F[,F]             Timeouts for initial evaluation and for pending
                              checks, in seconds. If the latter is omitted, it
                              is considered to be equal to the former one.
  --propagate-sigint          If set, litrepl will catch and resend SIGINT
                              signals to the running interpreter. Otherwise it
                              will just terminate itself leaving the
                              interpreter as-is.
  -d INT, --debug INT         Enable (a lot of) debug messages.
  --verbose                   Be more verbose (used in status).
  -C DIR, --workdir DIR       Set the working directory before execution. By
                              default, it uses LITREPL_WORKDIR if set,
                              otherwise remains the current directory. This
                              affects the directory of a new interpreter and
                              the --<interpreter>-auxdir option.
  --pending-exitcode INT      Return this error code if whenever a section
                              hits tim