Toplevel answers for long strings are not correct

[triska]

Currently, we get:

?- Ls = "This is a rather long string which is shortened by the toplevel.".
   Ls = "This is a rather lo ...".

The answer suggests that Ls is "This is a rather lo ...", but that is not true.

Shortening of long strings must be done in such a way that it is clear that this is not the actual solution.

The suggestion is to take inspiration from Ciao, using || to separate the shown prefix from the ellipsis.

Example:

?- Ls = "This is a rather long string which is shortened by the toplevel.".
   Ls = "This is a rather long s"||... .

Such an answer cannot be pasted back, which is the point.

[bakaq]

Really stupid idea, but what about:

?- Ls = "This is a rather long string which is shortened by the toplevel.".
   phrase(("This is a rather long s",...), Ls).

It's more general than the query, but can be pasted back (assuming library(dcgs) is loaded).

[hurufu]

Another solution would be to display truncated strings similarly to other lists:

?- Ls = "This is a rather long string which is shortened by the toplevel.".
   Ls = ['T',h,i,s,' ',i,s,' ',a,' ',r,a,t,h,e,r,' ',l,o|...].

[UWN]

... phrase(("This is a rather long s",...), Ls).

Pasting this back results in a non-terminating query. So if at all, it would be rather phrase("This is a rather long s",Ls,...). which assumes that DCGs have been loaded.

[UWN]

Some examples of double bar notation:

?- L="a"||"b"||"c".
   L = "abc".

?- L=""||""||""||K.
   L = K. 

?- L=("")||K.
   syntax_error(...).

?- L=[]||K.
   syntax_error(...).

Also, it would be now possible to split a string into multiple lines by still allowing
some layout inbetween.

   p( "this here\n"||
        "some more").