scryer

This is a Typescript package that embeds Scryer Prolog.

Experimental, API will change. Currently it's (roughly) based on trealla-js's API.

``
npm install scryer
`

`typescript
import { init, Prolog } from "scryer";

await init();

const kb1 =
:- use_module(library(format)).
:- use_module(library(clpz)).
:- use_module(library(lists)).

sudoku(Rows) :-
length(Rows, 9), maplist(same_length(Rows), Rows),
append(Rows, Vs), Vs ins 1..9,
maplist(all_distinct, Rows),
transpose(Rows, Columns),
maplist(all_distinct, Columns),
Rows = [As,Bs,Cs,Ds,Es,Fs,Gs,Hs,Is],
blocks(As, Bs, Cs),
blocks(Ds, Es, Fs),
blocks(Gs, Hs, Is).

blocks([], [], []).
blocks([N1,N2,N3|Ns1], [N4,N5,N6|Ns2], [N7,N8,N9|Ns3]) :-
all_distinct([N1,N2,N3,N4,N5,N6,N7,N8,N9]),
blocks(Ns1, Ns2, Ns3).
;

const kb2 =
problem(1, [[_,_,_,_,_,_,_,_,_],
[_,_,_,_,_,3,_,8,5],
[_,_,1,_,2,_,_,_,_],
[_,_,_,5,_,7,_,_,_],
[_,_,4,_,_,_,1,_,_],
[_,9,_,_,_,_,_,_,_],
[5,_,_,_,_,_,_,7,3],
[_,_,2,_,1,_,_,_,_],
[_,_,_,_,4,_,_,_,9]]).
;

const pl = new Prolog();
pl.consultText(kb1);
pl.consultText(kb2);

const query = pl.query(
"problem(1, Rows), sudoku(Rows), maplist(portray_clause, Rows).",
);
for (const answer of query) {
console.log(answer.bindings);
}
`

For browsers, you can use esm.sh or other CDNs to import it directly:

`html

`

Usage

$3

`typescript
const answer = pl.queryOnce("X is Y * 2.", { bind: { Y: 21 } });
console.log(answer.bindings); // { X: 42, Y: 21 }
`

$3

The prolog string template literal is an easy way to escape terms.
Each ${value} will be interpreted as a Prolog term.

`typescript
import { prolog, Variable } from "scryer";
const answer = pl.queryOnce(
prologatom_chars(${new Variable("X")}, ${"Hello!"}).,
);
console.log(answer.bindings); // { X: Atom('Hello!') }
`

$3

Prolog instances are subclasses of EventTarget and emit the following events:

- "ready" -- fired when a query finishes and the interpreter is ready to execute a new query

Development

After cloning the repository, make sure to initialize the submodules:

`bash
git submodule update --init --recursive
`

Alternatively, you can do this directly during the clone:

`bash
git clone --recurse-submodules -j8
`

make sure to have wasm-pack installed.

Once the submodules are in place and wasm-pack is installed, run the following commands:

`bash
npm install
npm run compile # Installs the WASM package of Scryer Prolog and other dependencies
npm run build # Transpiles TypeScript code
``