Re: How Prolog became an education nightmare (Was: 50 Years of Prolog Nonsense)

Here is the SWI-Prolog and the SICStus
Prolog abstract parse term. This is the real
nightmare of every computer science professor,
who wants to use Prolog in a compiler
construction course:
/* SWI-Prolog 9.3.14 */
end(end(begin(;(=(x,1),;(=(y,2),begin(=(z,3)))))))
/* SICStus Prolog 4.9.0 */
begin(;(=(x,1),;(=(y,2),begin(end(end(=(z,3)))))))
On the other hand mostlikely the OP @horsh
would expect:
/* What the End-User wants */
end(begin(;(=(x,1),;(=(y,2),end(begin(=(z,3)))))))
I think its impossible to do in any Prolog system,
you would need a programming language with the
possibility to do mixfix syntax definitions,
like for example in Isabelle/HOL:
(* Define the mixfix syntax for a Pascal-like block *)
syntax
   "_begin_end" :: "'a ⇒ 'a" ("begin _ end")
Or otherwise use DCG to write your own parser
for the DSL at hand, that you want to parse.
Since Prolog operators cannot model mixfix syntax,
at least SWI-Prolog and SICStus Prolog fail,
and I guess other Prolog systems fail as well.
Mild Shock schrieb:

Concerning the input (xxx yyy zzz) the OP wrote:
 I would expect it to print zzz(xxx(yyy)).
 Where did he get this requirement from, he didn’t
compare other Prolog systems, right? So it came from
his applicationdomain. But what was his application
 domain? Ok, lets proceed to an example with multiple
brakets. Lets make the Pascal “begin” “end” example,
by replacing xxx and zzz by “begin” and “end”.
 I get this result:
 ?- member(X,[begin,end]), current_op(Y,Z,X).
X = (begin), Y = 1100, Z = fy ;
X = (end), Y = 1100, Z = yf.
 ?- X = (begin
|          x = 1;
|          y = 2;
|          begin
|               z = 3
|          end
|       end).
X = (begin x=1;y=2;begin z=3 end end).
 But is the abstract parse term, the Prolog result useful?