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# [Tiny-Prolog-in-OCaml](https://github.com/Naereen/Tiny-Prolog-in-OCaml)
> A tiny implementation of a small subset of the Prolog language, in OCaml. With small and fun examples.
>
> WARNING: this project only has an **educational purpose**, for a real-world use of Prolog, please refer to [GNU Prolog (gprolog)](XXX).
This project contains [the code](prolog/) and [examples](examples/) for a tiny [Prolog](https://en.wikipedia.org/wiki/Prolog) implementation, written in [the OCaml language](https://ocaml.org/).
- See [this folder](prolog/) for instructions to build the project (really easy: clone, run `make`, relax and enjoy :tada:). The implementation focuses on a very small subset of Prolog, see the examples for a good idea of what is supported.
- See [this other folder](examples/) for examples (in English).
## Example
- A theory has this form, first with axioms (predicate):
```prolog
cat(tom).
mouse(jerry).
```
- Then maybe some rules, stating that [a mouse is fast and a cat can be stupid](https://en.wikipedia.org/wiki/Tom_and_Jerry):
```prolog
fast(X) <-- mouse(X).
stupid(X) <-- cat(X).
```
- If you save this file (see [this example](examples/tomandjerry.pl)), you can then load it with the `prolog` binary:
```bash
$ ./prolog/prolog ./examples/tomandjerry.pl
?- stupid(tom).
{ }
continue ? (o/n) [o] :
```
- This `{ }` is an empty model, meaning that `stupid(tom).` evaluates to True in an empty model (no need for instanciation).
- You can also ask your question directly in the command line:
```bash
$ ./prolog/prolog ./examples/tomandjerry.pl "fast(tom)."
?- fast(tom).
```
- An empty response mean that the term is false, no matter the model.
- You can add more rules, as you want.
```prolog
ishuntedby(X, Y) <-- mouse(X), cat(Y).
```
```bash
$ ./prolog/prolog ./examples/tomandjerry.pl "ishuntedby(tom, jerry)."
?- ishuntedby(tom, jerry).
$ ./prolog/prolog ./examples/tomandjerry.pl "ishuntedby(jerry, tom)."
?- ishuntedby(jerry, tom).
{ }
```
- You can also add comments, that are lines starting with one or more `#` character.
```prolog
# the mouse always espace the cat!
istrickedby(X, Y) <-- cat(X), mouse(Y).
```
## More example
- See [this folder](examples/),
- Or [this notebook](example.ipynb).
---
### :scroll: License ? [](https://github.com/Naereen/Tiny-Prolog-in-OCaml/blob/master/LICENSE)
This (small) repository is published under the terms of the [MIT license](http://lbesson.mit-license.org/) (file [LICENSE](LICENSE)).
© [Lilian Besson](https://GitHub.com/Naereen), 2018.
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