Re: Ann: SWI-Prolog 7.1.0

Hi Jan

Sorry for being ignorant, but I can't understand example with multi-lists from 
documentation:

> Using '[]' as list terminator prevents dynamic distinction between atoms and lists. 
As a result, we cannot use type polymorphism that involve both atoms and lists. 
For example, we cannot use /multi lists/ (arbitrary deeply nested lists) of atoms. 
Multi lists of atoms are a in some situations a good representation of a flat list that 
is assembled from sub sequences. The alternative, using difference lists or DCGs is 
often less natural and sometimes demands for `opening' proper lists (i.e., copying 
the list while replacing the terminating empty list with a variable) that have to be 
added to the sequence.

Could you please give some simple example.


On Friday 22 November 2013 16:36:56 Jan Wielemaker wrote:
> Hi,
> 
> I have uploaded SWI-Prolog 7.1.0. As the major release indicates, this
> makes SWI-Prolog a different system. You find more elaborate
> documentation including motivations in the chapter "SWI-Prolog
> extensions" in the manual.
> (http://www.swi-prolog.org/pldoc/man?section=extensions).
> 
> I understand that this move will make some users deeply unhappy. I am
> also convinced that (SWI-)Prolog badly needed some refreshment that
> enables smoother integration with modern IT platforms while making the
> language appear more natural to new users. The key issue is that
> many of us need a language to write applications that talk to other
> systems and not only a language that can "solve N-queens very elegantly,
> but in splendid isolation". Don't worry, it can still solve N-queens
> very elegantly, especially using Markus' clp(fd).
> 
> I would like to thank all people that provided feedback on the original
> proposal.
> 
> Vitor Santos Costa has expressed that he likes most aspects of the
> current proposal, which makes it likely that YAP users can enjoy
> these gadgets too at some point in the future.
> 
> Below are the highlights:
> 
>    - Lists are no longer represented as .(H,T).  Instead, the list
>      functor is now '$cons'(H, T).  The empty list is still [], but
>      this is not an atom.  I.e., '[]' == [] fails.
> 
>    - By default, double quoted "text" is mapped to an object of type
>      string.  This already raised some discussions.
> 
>    - The system introduces `maps' as primary citizens.  Maps are
>      collections of key-value pairs, optionally typed. Maps are
>      supported by read and write.  The syntax is
> 
> 	type{key1:value1, key2:value2, ...}
> 
>      Keys in a map can be addressed using the functional notation
>      Map.Key.  User functions on maps can be accessed as Map.Compound
>      (e.g., Vector.multiply(V2)).
> 
>    - Quoted atoms are no longer operators.
> 
>    - Unquoted atoms may contain internal dots.  E.g., a.b is an
>      atom.
> 
>    - functor() is valid syntax.  It produces a term that is distinct
>      from 'functor'.  The `block' operator '()' to hack this syntax
>      has been removed.
> 
>    - The `block' operators [] and {} remain.
> 
> Most of this can be disabled using "swipl --traditional". Notable this
> gets the old list datastructure and "text" as a list of character codes.
> It also disables functional notations on maps. The other syntax
> extensions remain valid as they do not cause incompatibilites by
> themselves.
> 
> I expect the system to run fairly stable.  Depending on feedback, there
> could be minor changes to the extensions.  Certainly, there will be more
> predicates operating on strings and maps and more of the libraries will
> be prepared to work with these extensions.
> 
> 
> 	Enjoy --- Jan
> 
> 
> ========================================
> SWI-Prolog Changelog since version 6.5.3
> ========================================
> 
>   * CLEANUP: Renamed `meta_atom' into `reserved_symbol'.  This is a mostly
>     internal name, only showing up when using blob/2 on [].
> 
>   * FIXED: edit/0: file detection and edit/1: allow for file.<ext>
> 
>   * FIXED: Map.put(New).
> 
>   * FIXED: specify access as access([read,write]).  Map-based option
>     processing does not allow for multiple options with the same name.
> 
>   * ADDED: Make set_stream(S, file_name(Name)) accept a string a Name.
> 
>   * ADDED: read_term/2 option dot_lists(Bool) to read lists in traditional
>     canonical syntax.
> 
>   * MODIFIED: Deleted PL_WRT_LIST from SWI-Prolog.h.  This is no longer
>     used.
> 
>   * FIXED: char_type(X, prolog_atom_start)
> 
>   * DOC: Added desction on when to use which representation for text.
> 
>   * ADDED: Colour support for maps.
> 
>   * ADDED: Finished subterm position representation for maps
> 
>   * DOC: Added new operators to the table
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