agda-kernel 0.3

A rudimentary Jupyter kernel for Agda

[](https://mybinder.org/v2/gh/lclem/agda-kernel/master)
[](https://travis-ci.org/lclem/agda-kernel)
[](https://github.com/jupyter/notebook/releases/tag/5.7.8)
[](https://github.com/agda/agda/releases/tag/v2.5.4.2)
[](https://github.com/agda/agda-stdlib/releases/tag/v0.17)

# agda-kernel
An experimental Agda kernel for Jupyter.

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

pip install agda_kernel
python -m agda_kernel.install

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``.
It needs to be manually installed inside Jupyter, as follows:
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

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

Each code cell must begin with 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 result of typechecking the cell are then displayed.

After a cell has been evaluated, one can

- Infer the type of a closed expression,
by putting the cursor near the expression and hitting 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 |
| \[= | ⊑ |