README.md

Rolas
=====

Rolas is a simple database for music. It can mine a music folder for the
database, and it can also show and play the tracks and do queries on them.

Compiling and running it
------------------------

To compile `rolas` you need [`meson`](https://mesonbuild.com/) and
[`ninja`](https://ninja-build.org/) installed.

```
git clone https://aztlan.fciencias.unam.mx/gitlab/canek/rolas.git
cd rolas/
meson build/
ninja -C build/
```

The executable will be in `buid/rolas`, and you should be able to run it from
anywhere.

```
./bin/rolas
```

To run the tests you need to be in the project directory.

```
ninja -C build/ test
```

Grammar
-------

The grammar for the query language is shown here in
[Backus–Naur form](https://en.wikipedia.org/wiki/Backus%E2%80%93Naur_form):

```
<expr> ::= <match> | (<expr>) | <unaryop><expr> | <expr><binaryop><expr>

<match> ::= <field> ":" <string>

<field> ::= "title" | "titl" | "tit" | "ti" | "t" |
            "artist" | "artis" | "arti" | "art" | "ar" | "a" |
            "album" | "albu" | "alb" | "al" | "l"

<string> ::= [:alpha:]+ | "\""[^\"]+"\""

<unaryop> ::= "!"

<binaryop> ::= "&" | "|"
```

To avoid ambiguity, the binary operators associate to the left; in other words:

```
t:love & a:john | l:hits
```

is interpreted as:

```
(t:love & a:john) | l:hits
```