Re: internal vs external representation

On Sun, 2014-04-13 at 11:07 -0700, Ross Boylan wrote:
> Essentially I'm looking for a kind of reverse of portray. Portray goes
> from an internal representation (for prolog) to an external
> representation (for a person).  I'd like to go from user input in the
> external form to the internal form.
> 
> Following Richard O'Keefe's advice I used structurally explicit forms
> for some of my constructs.  An auxiliary program (in python) converts
> from a friendlier form of input, so
> input (external representation) -> internal representation
> 3/1/12 -> when(date(2012, 3, 1), seq(0))
> myos~/a/b/c -> path([myos, a, b, c]).
> 
> portray then does the reverse mapping (even in the debugger, which is
> quite nice).
> 
> My question is how I can get the first mappings for interactive queries.
> E.g., now I must type
> deep_descendants(path([oscorn1, usr, local, root]), when(date(2011,12,
> 28), seq(999)), G)
> to get G (a graph).
> 
> I would like to be able to type
> deep_descendants(oscorn1~/usr/local/root, 12/28/11#9999, G).
> 
> Is there a way to do that, or something close to it?
> 
> Maybe with some kind of helpers, e.g.,
> make_when(12/28/11#9999, When), make_path(oscorn1~/usr/local/root,
> Path), deep_descendants(Path, When, Graph).
> But that's a little clunky, and maybe the arguments need to be strings.
> 
Here's some code for the slightly clunky version.  Defining operators
avoids the need to quote, and lets prolog do the parsing for me.

:- op(400, yfx, #).

make_when(M/D/Y1#S, when(date(Y2, M, D), seq(S))) :-
	Y2 is Y1 + 2000.

make_when(M/D/Y1, when(date(Y2, M, D), seq(S))) :-
	make_when(M/D/Y1#0, when(date(Y2, M, D), seq(S))).

% making ~ an operator didn't work
make_path(A/B, path(PathList)) :-
	make_path(A, path(P2)),
	append(P2, [B], PathList),
	!.

make_path(A, path([A])).

When I tried declaring ~ an operator I got this:

?- make_path(os~/a/b/c, P).
ERROR: Syntax error: Operator expected
ERROR: make_path(os
ERROR: ** here **
ERROR: ~/a/b/c, P) . 

So I'm just using slashes on input paths.
Ross