agda-kernel 0.64
A rudimentary Jupyter kernel for Agda

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# agda-kernel
An experimental Agda kernel for Jupyter.
Used at [Nextjournal](https://nextjournal.com/plfa/ToC) [[nextjournal kernel]](https://github.com/nextjournal/agda-kernel).

![](demo/demo1.gif)

Examples
--------

You can launch the following examples directly via the mybinder interface:

<!-- - [example/Lab01.ipynb](https://github.com/lclem/agda-kernel/blob/master/example/Lab01.ipynb) [[binder]](https://mybinder.org/v2/gh/lclem/agda-kernel/master?filepath=/example/Lab01.ipynb).

- [example/Lab02.ipynb](https://github.com/lclem/agda-kernel/blob/master/example/Lab02.ipynb) [[binder]](https://mybinder.org/v2/gh/lclem/agda-kernel/master?filepath=/example/Lab02.ipynb).

- [example/Lab03.ipynb](https://github.com/lclem/agda-kernel/blob/master/example/Lab03.ipynb) [[binder]](https://mybinder.org/v2/gh/lclem/agda-kernel/master?filepath=/example/Lab03.ipynb).

-->

- [example/LabImp.ipynb](https://github.com/lclem/agda-kernel/blob/master/example/LabImp.ipynb) [[binder]](https://mybinder.org/v2/gh/lclem/agda-kernel/master?filepath=example/LabImp.ipynb).

Alternatively, if you have [binder](https://github.com/jupyterhub/binderhub),
then you can use [repo2docker](https://github.com/jupyter/repo2docker) locally:

    repo2docker https://github.com/lclem/agda-kernel

Installation
------------

    pip install agda_kernel
    python -m agda_kernel.install

### Syntax highlighting

Syntax highlighting is done separately by [Codemirror](https://codemirror.net/),
but unfortunately there is no Agda mode packaged with it.
A rudimentary Agda mode for Codemirror can be found in ``codemirror-agda/agda.js``.
In order to install it, type

    make codemirror-install
    
<!-- or follow the manual instructions below:
Let `dir` be the result of executing the following command

    pip show notebook | grep Location | cut -d ' ' -f 2

(It is something like ``/usr/local/lib/python3.7/site-packages``,
``~/anaconda3/lib/python3.7/site-packages``,
or  ``/usr/local/Cellar/jupyter/1.0.0_5/libexec/lib/python3.7/site-packages/``.)
Then, 

    mkdir -p dir/notebook/static/components/codemirror/mode/agda
    cp codemirror-agda/agda.js dir/notebook/static/components/codemirror/mode/agda
-->

### Agda extension

In order to improve the Jupyter interface,
it is strongly recommended to also install [`agda-extension`](https://github.com/lclem/jupyter_contrib_nbextensions).

Functionality
-------------

Each code cell must contain a line of the form ``module A.B.C where``.
For instance:

```agda
module A.B.C where

id : {A : Set} → A → A
id x = x
```

Upon execution, the file `A/B/C.agda` is created containing the cell's contents,
and it is fed to the Agda interpreter (via `agda --interaction`).
The results of typechecking the cell are then displayed.

After a cell has been evaluated, one can

- Run Agsy (auto) by putting the cursor next to a goal `?` and hitting TAB.
The hole `?` is replaced by the result returned by Agsy, if any,
or by `{! !}` if no result was found.
If there is more than one result, the first ten of them are presented for the user to choose from.

- Refine the current goal by putting the cursor next to a goal `{! !}` and hitting TAB.
An optional variable can be provided for case-splitting `{! m !}`.

- Show information about the current context, goal, etc.: putting the cursor near a goal/literal and hit SHIFT-TAB.
<!--If the expression is in parentheses ``(...)``, then the cursor should be near one of the two parentheses.
If the expression is just a literal, then the cursor should be inside, or in the vicinity of the literal.

- Normalise a closed expression,
by putting the cursor near the expression and hitting TAB.
Expression localisation follows the same rules as in the previous point.
-->

Editing
-------

Inputting common UNICODE characters is facilitated by the code-completion feature of Jupyter.

- When the cursor is immediately to the right of one of the `base form` symbols
hitting TAB will replace it by the corresponding `alternate form`.
Hitting TAB again will go back to the base form.

| base form | alternate form |
|:---------:|:----------------:|
| -> | → |
| \ | λ |
| < | ⟨ |
| B | 𝔹 |
| > | ⟩ |
| = | ≡ |
| top | ⊤ |
| /= | ≢ |
| bot | ⊥ |
| alpha | α |
| /\ | ∧ |
| e | ε |
| \/ | ∨ |
| emptyset | ∅ |
| neg | ¬ |
| qed | ∎ |
| forall | ∀ |
| Sigma | Σ |
| exists | ∃ |
| Pi | Π |
| \[= | ⊑ |