# Introduction

This is the website for PProlog, a new prolog implementation written
in C on and for plan 9 (9front specifically). Work started in december 2020
due to the author's need for a prolog system on 9front. The long term goal 
is to be compliant with the ISO standard but currently it is all just
experimentation.

# Features

* A base system based on the WAM (Warren abstract machine) implemented by following the book [here](http://wambook.sourceforge.net/wambook.pdf).
* Support for extended precision arithmetic via [mp(2)](http://man.9front.org/2/mp).
* Basic support for definite clause grammars (DCGs). For now DCG's are translated by the parser into difference lists and they do not support everything one expects.
* Lists.
* Strings represented as list of char atoms.
* The basic control predicates such as `,/2`, `;/2`, `->/2` and cut.
* Full unicode support.

# Status

At this moment the system works OK but it has very few builtin predicates
and much of what people expect from a working prolog system is still missing.

The list of builtins as of January 13, 2021 is:

* `is/2`
* `halt/0`
* `consult/1`
* `write/1`
* `read/1`
* `call/n`
* `fail/0`
* `>/2`
* `==/2`
* `atom/1`
* `integer/1`
* `float/1`
* `var/1`
* `compound/1`
* `term_variables/2`

And the following predicates are implemented in the standard library:

* `=/2`
* `\=/2`
* `reverse/2`
* `samelength/2`
* `append/3`
* `member/2`
* `select/3`
* `length/2`
* `nl/0`
* `phrase/2`
* `\+/2`
* `false/0`
* `true/0`
* `repeat/0`
* `once/1`
* `,/2`
* `;/2`
* `->/2`
* `=\=/2`

and many more all listed [here](https://git.sr.ht/~pmikkelsen/pprolog/tree/master/item/stdlib.pl).