7 Standard Prolog Compliance

SICStus 3.8 supports standard Prolog, adhering to the International Standard ISO/IEC 13211-1 (PROLOG: Part 1—General Core) (http://webstore.ansi.org/ansidocstore/product.asp?sku=INCITS%2FISO%2FIEC+13211%2D1%2D1995). At the same time it also supports programs written in earlier versions of SICStus. This is achieved by introducing two execution modes iso and sicstus. Users can change between the modes using the Prolog flag language. Main issues:

• The sicstus execution mode is practically identical to 3.7.1, except for minor changes in error term format.
• The iso mode is fully compliant with ISO standard, but no strict conformance mode is provided.
• The dual mode system supports the gradual transition from legacy SICStus code to ISO Prolog compliant programs.
• Note that the built-in predicates, functions and Prolog flags, required by the ISO standard, are also available in sicstus execution mode, unless they conflict with existing SICStus predicates or functions. This expansion of the language carries a remote risk of name clashes with user code.