.TH mode 1 "September 7, 1994"
.SH NAME
mode \- declare mode of call for predicates that can appear in a hypothesis
constructed by
.I Progol.
.SH SYNOPSIS
.B modeh(RecallNumber,HeadTemplate)?
.B modeb(RecallNumber,BodyLiteralTemplate)?
.SH DESCRIPTION
.B
modeh/2
and 
.B
modeb/2  describe the `forms' of literals that are allowed
in the head and body of a hypothesised clause.
.I RecallNumber
specifies an upper bound on the number of successful calls
to the predicate specified in the mode declaration.
.I HeadTemplate
specifies all legal forms for a head literal in a
clause constructed by
.I
Progol.
.I BodyLiteralTemplate
specifies all legal forms for a body literal in a
clause constructed by
.I
Progol.
.SH OPTIONS
.I RecallNumber
can be either 
.TP
.B a number
specifying an upper bound number of successful calls to the predicate
.TP
.B *
specifying that the number of successful calls to the predicate
is bounded above by some large integer value (currently 100).
.TP
.I HeadTemplate, BodyLiteralTemplate
are predicate templates of the form
.TP
.B p(ArgSpec, ArgSpec,...)
where, for each argument 
.I ArgSpec
is of the form
.I Mode Type
or
.I f(ArgSpec, ArgSpec,...)
where f is a function symbol.
In the former,
.I Mode Type
is specified as follows.
.I Mode
is one of the following
.ne 12
.RS
.TP
.B +
indicates the argument is an input. That is, in all calls to this
predicate, the argument will be bound to a value.
.TP
.B -
indicates the argument is an output. That is, in all calls to this
predicate, the argument will output a term.
.TP
.B #
indicates that a constant should appear in this argument.
.RE
.TP
.I Type
is the type of the argument. Types are unary predicates defined
in the background knowledge, or Prolog built-in functions.
.TP
There can be more than one mode of call for each predicate name.
.SH EXAMPLES
Here are some example of specifying modes:
.DS 3 1
modeh(1,mem(+number,[+number|+list]))?
modeb(1,mem(+number,+list))?

modeb(1,dec(+integer,-integer))?
modeb(1,mult(+integer,+integer,-integer))?
modeb(1,plus(+integer,+integer,-integer))?
modeb(1,+integer=#integer)?

modeb(*,has_car(+train,-car))?
.DE
.SH "SEE ALSO"
types