Show HN: Prolog compiler and interpreter in pure JavaScript

#1

Post by jldupont » Sun, Oct 25, 2015, 12:40 AM UTC

Show HN: Prolog compiler and interpreter in pure JavaScript
prolog.jldupont.com

Re: Show HN: Prolog compiler and interpreter in pure JavaScript

#2

Post by colanderman » Sun, Oct 25, 2015, 2:43 AM UTC

    ?- X = 10.
    X = _
    no.

...this doesn't work like any Prolog I know. (Even defining equality manually as "eq(X, X)." doesn't work...)

Re: Show HN: Prolog compiler and interpreter in pure JavaScript

#3

Post by dmytrish » Sun, Oct 25, 2015, 4:11 PM UTC

colanderman wrote: post #2

?- X = 10. X = _ no. ...this doesn't work like any Prolog I know. (Even defining equality manually as "eq(X, X)." doesn't work...)

Why? `?-` indicates that it's a query, it should not define anything.

Re: Show HN: Prolog compiler and interpreter in pure JavaScript

#4

Post by colanderman » Mon, Oct 26, 2015, 4:15 AM UTC

dmytrish wrote: post #3

colanderman wrote: post #2

?- X = 10. X = _ no. ...this doesn't work like any Prolog I know. (Even defining equality manually as "eq(X, X)." doesn't work...)

Why? `?-` indicates that it's a query, it should not define anything.

    $ swipl
    ?- X = 10.
    X = 10.

    $ gprolog
    | ?- X = 10.
    X = 10
    yes

(a) The REPL should print the variable bindings which caused the query to succeed. (b) The query `X = 10.` should succeed trivially.

I've been using Prolog on-and-off for close to a decade now and have implemented my own pseudo-Prolog (also in Javascript; was missing logic variables and extra-logical builtins). I tried to get pretty much any query to succeed in this interpreter and couldn't. This is not any kind of Prolog that I'm familiar with.

Re: Show HN: Prolog compiler and interpreter in pure JavaScript

#5

Post by dmytrish » Mon, Oct 26, 2015, 4:20 PM UTC

colanderman wrote: post #4

dmytrish wrote: post #3

Earlier quoted context omitted.

Why? `?-` indicates that it's a query, it should not define anything.

$ swipl ?- X = 10. X = 10. $ gprolog | ?- X = 10. X = 10 yes (a) The REPL should print the variable bindings which caused the query to succeed. (b) The query `X = 10.` should succeed trivially. I've been using Prolog on-and-off for close to a decade now and have implemented my own pseudo-Prolog (also in Javascript; was missing logic variables and extra-logical builtins). I tried to get pretty much any query to succee…

Yep, I agree I was wrong (having too little experience in Prolog): variables are necessary to extract values from queries.