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From - Fri Sep 24 13:22:41 1999
Message-ID: <md5:71827EBD26CDFC50070A4480CB75606A>
Date: Fri, 27 Mar 92 17:40:16 +0100
From: Micha Meier <micha@scorpio>
To: joachim
Subject: builtin types
Content-Length: 1702
Status: RO
X-Lines: 59

For each builtin pred which is written in C and does not backtrack, its
type is stored in the mask 0x1c of its flags. The types are:

#define U_NONE          0x00000000L  no unification; most of them have
	entry modes ++, but some don't, e.g. tests. Those that can succeed
	with nonground modes are:

@</2 etc.
\==/2
als_/2
assert_/2
asserta_/2
compile_term_/2
compound/1
display/2
instance/2
is_compound/1
meta/1
meta_older/1
nonground/1
nonvar/1
occurs/2

#define U_SIMPLE        0x00000004L - bind one argument to a constant.
Some may have nonground exit modes, e.g. compare/3 etc.

#define U_GROUND        0x00000008L - one or more argument are bound to
	ground structures, or several arguments are bound to constants
	(i.e. more than one variable can be bound in these predicates
	to ground terms). I think all have ground exit modes (?)


#define U_UNIFY         0x0000000cL - predicates that unify two arguments
	or their parts with each other, or unify one argument with
	a possibly nonground structure. The exit mode depends on the input modes
	of the unified arguments.


#define U_GLOBAL        0x00000010L - may unify an argument with a term
	that contains variables, which do not occur in the caller but
	may occur elsewhere. These are mostly delay_goals etc.


#define U_DELAY         0x00000014L - a delay condition

The type can be obtained by proc_flags(N/A, 1, Flags, Module), Flags /\ 16'1c
The info about bound arguments can be obtained by
	bound_arg_(N/A, I, Binding, Module),

e.g.
[sepia_kernel]: bound_arg_(arg/3, 3, X, sepia_kernel).

X = nonvar
yes.
[sepia_kernel]: bound_arg_(get/1, 1, X, sepia_kernel).

X = constant

It fails if the argument is not changed by the builtin.