Changes in Release 3

• Backslashes (\) in strings, quoted atoms, and integers written in 0' notation denote escape sequences. Character escaping can be switched off.
• Multifile declarations are required in all files where clauses to a multifile predicate are defined. This complies with the ISO Prolog Standard.
• The built-in predicate call_residue/2 has been modified so that goals that are disjunctively blocked on several variables are returned correctly in the second argument.
• The built-in predicate setarg/3 has been removed. Its functionality is provided by the new built-in predicates create_mutable/2, get_mutable/2, update_mutable/2, and is_mutable/2, which implement a timestamp technique for value-trailing with low-level support.
• The built-in predicates unix/1 and plsys/1 have been removed. Their functionality is provided by prolog_flag(argv,X), by the new halt/1 built-in predicate, and by the new library(system) module, which also contains several new predicates.
• The socket I/O built-in predicates have been moved to the new library(sockets) module.
• The built-in predicate time_out/3 has been moved to the new library(timeout) module.
• The built-in predicates term_hash/[2,4], subsumes_chk/2, and term_subsumer/3 have been moved to the new library(terms) module, which also contains operations for unification with occurs-check, testing acyclicity, and getting the variables of a term.
• The foreign language interface (Prolog-to-C) has been extended with the types +chars, -chars and [-chars] for fast conversion between C strings and Prolog code-lists. Several new interface functions are available.
• The memory handling of the C-to-Prolog interface has been simplified by passing each Prolog term as a "handle" object, called an SP_term_ref, making the functions SP_show_term() and SP_hide_term() obsolete.
• The InterViews 2.6 based GUI module library(gmlib) has been replaced by the Tcl/Tk based library(tcltk). A version of library(gmlib) converted to SICStus Prolog release 3 is available from ftp://ftp.sics.se/archive/sicstus3/gmlib.tar.gz.
• The library(objects) module has been enhanced.
  • Inheritance is static, i.e. determined at object creation time, and is implemented as module importation.
  • A new, very light-weight, type of object: instance.
  • Attributes, efficient storage of terms in objects.
  • Unprefixed goals in methods denote message passing to self. Prolog goals in methods must be prefixed by :.
• In library(charsio), the open_chars_stream/[3,4] predicates have been replaced by open_chars_stream/2 and with_output_to_chars/[2,3].
• The library(assoc) module now implements AVL trees instead of unbalanced binary trees.
• The new library(atts) implements attributed variables, a general mechanism for associating logical variables with arbitrary attributes. Comes with a number of hooks that make it convenient to define and interface to constraint solvers.
• The Boolean constraint solver has been moved to the new library(clpb) and is implemented on top of library(atts).
• New constraint solvers for rationals (library(clpq)) and reals (library(clpr)), implemented on top of library(atts).
• user:goal_expansion/3 is a new hook predicate for macro-expansion.
• bb_put/2, bb_get/2, bb_delete/2, and bb_update/3 are new built-in predicates implementing blackboard primitives.
• prolog_load_context/2 is a new built-in predicate for accessing aspects of the context of files being loaded.
• user:file_search_path/2 is a new hook predicate providing an path expansion mechanism for filenames.
• gcd/2 is a new built-in function.
• The statistics keyword walltime measures elapsed absolute time.
• In runtime systems, ensure_loaded/1 and use_module/[1,2,3] have the same semantics as in development systems.
• Native code compilation available for MIPS platforms.
• Problems in native code compilation for certain SPARC models have been eliminated.
• Performance improvements include emulated code speed, native code speed, and the foreign language interface.
• The system has been ported to the DEC OSF/1 Alpha (a 64-bit platform).