Re: Announcement: Homage to SWI-Prolog

On 25/07/2013, at 5:17 AM, Torbjörn Lager wrote:
> Richard> In deleting the query I had typed, I was dismayed to see that
> the "?-" went too.  Had I completely broken the thing?  Would any
> query ever work again.  (_Serious_ question.  I genuinely believed it
> possible that the interface would not work again.)
> 
> It is hard to do much about that. That is why I provide the Clear
> button underneath the query field instead.

(a) Would it work to put the "?-" and "|:" prompts *outside* the
    edit boxes?  I've used a Prolog on the old Mac that did something
    like that.

(b) I am sorry, but while "Clear" is a good reminder for people who
    _already_ know what the button does, it doesn't clue in people
    who don't.  I thought it would probably erase the transcript window
    above.
> 
> Richard> Finally despairingly I click on "Solve": in 34 happy Prolog
> years I've never heard "Solve" used for this
> before.
> 
> Must say I find it a bit odd you haven't heard "solve" in the context
> of "solve a goal".

Yes, but "solving a goal" is a repeated step in "executing a query".
I've seen "Run", "Query", "Ask", "Do it!" and some others.

> Richard> Typing a query in one box (so that my eyes have to be
> pointing down there) and then having the answers appear way up
> somewhere else reminds me of the old Apollo interface, which I
> couldn't get away from fast enough.
> 
> I contemplated implementing a more conventional command line interface
> but it somehow felt weird to have that in a browser.

Weird schmeird.  It's a basic user interface issue: all the stuff the
user has to concentrate on should be happening where the user is looking,
if that's practical.   I didn't say "I want a conventional command line
interface".  What I want is the query and answer to be _close_.  For
example, the box could be _just above_ the place where the answers come out.
> Richard> The syntax colouring is weird.
> 
> Yes, I'm aware of that. It even says so in the Help section under
> Issues.

Yes BUT.  It is better to have *NO* colouring than to have crazy colouring.
There is a very simple fix: leave it doing whatever syntax processing it
wants, but make the default colour for _everything_ black.

There is actually a fundamental issue here, which is that I don't think
you _can_ colour Prolog usefully without integration with a Prolog
processor.  The ACE colouring seems to be *trying* to make a 3-way
distinction:
 d. this is where an executable item is defined
 u. this is where an executable item is used
 t. this thing that looks like an executable item is data
That is a far more useful distinction than a distinction between
variables and constants -- if you can't tell the difference between a
capital letter and a small letter colouring isn't going to help much.
But you can't tell the difference between u and t without processing
:- meta_predicate declarations.

> JSFIDDLE and JS BIN seem to be used a lot, so maybe others want to use
> SWISH.

I dare say they will.  However, there's a big distinction.
JSFIDDLE is about HTML/CSS/Javascript, so there is something for
the Javascript code to act on.
Many of the small Prolog programs I write are there to read and
write files.  I _can't_ use a system that doesn't offer file I/O
for such programs.

Of course, that doesn't mean that the "files" that an example _thinks_
it is reading and writing have to be _real_ files...