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®10.2.13.1 Condition Meta-variable
This is where a variable appears as a goal in the body of a rule. The head of a clause
may not be represented in this way. By the time the meta-variable is called it must have
been instantiated to one of the following:
-
an atom (represents a call to a 0-argument relation).
- a compound term of the form:
relation( t1, t2, ..., tk)
The effect of evaluating a condition meta-variable is the same as if the condition had
appeared in the source program instead of the meta-variable.brackets (’{’ and ’}’).