Predicate Reference

The following predicates can be used to begin a statement.

`forall(Symbol, Predicate)`	The predicate is true if all instances have property. Use this predicate to start a constraint statement
`forany(Symbol, Predicate)`	Finds all instances which have property. Use this predicate to start a query statement.
`forn(Symbol, Predicate)`	??. Use this predicate to start a query statement.

`/=(Any, Any)`	The predicate is true if the two parameters are not equal
`<(Number, Number)`	The predicate is true if the first argument is less than the second argument.
`<=>(Predicate, Predicate)`	The predicate is true if left and right are equivalent, i.e. if they are both true or both false.
`=(Any, Any)`	The predicate is true if the two parameters are equal.
`=>(Predicate, Predicate)`	The predicate is true if assumption is false, or if both assumption and conclusion are true.
`>(Number, Number)`	The predicate is true if the first argument is greater than the second argument.
`allowed-slot-value(Slot, Class, Any)`	The predicate is true if value is allowed for the slot in the class.
`allowed-slot-value-type(Slot, Class, Class)`	The predicate is true if type is allowed for the slot in the class.
`and(Predicate, Predicate)`	The predicate is true when both predicates in the argument list are true.
`direct-instance-of(Frame, Class)`	The predicate is true if the first argument is a direct instance of the second argument.
`direct-subclass-of(Class, Class)`	The predicate is true if the first argument is the direct subclass of the second argument.
`direct-superclass-of(Class, Class)`	The predicate is true if the first argument is the direct superclass of the second argument.
`direct-template-slot-of(Slot, Frame)`	The predicate is true if the first argument is the direct template slot of the second argument.
`element-of(Any, Instance)`	The predicate is true if the instance is an element of the first parameter.
`even(Integer)`	The predicate is true if the integer is an even integer.
`exists(Symbol, Predicate)`	The predicate is true if there exists at least one instance which has property.
`facet-not-null(Facet, Frame, Slot)`	The predicate is true if the facet describing the slot is not null.
`instance-of(Frame, Class)`	The predicate is true if the frame is an instance of the class.
`is-class(Any)`	The predicate is true if the parameter is a class.
`is-concrete-class(Any)`	The predicate is true if the parameter is a concrete class.
`is-frame(Any)`	The predicate is true if the parameter is a frame.
`negative(Number)`	The predicate is true if the number is a negative number
`not(Predicate)`	The predicate is true if the argument predicate is false, and vice versa.
`odd(Integer)`	The predicate is true if the integer is an odd integer.
`or(Predicate, Predicate)`	The predicate is true if either predicate in the argument list is true.
`own-facet-not-null(Facet, Frame, Slot)`	The predicate is true if the facet describing the slot is not null.
`own-slot-not-null(Slot, Frame)`	The predicate is true if the slot belonging to the frame is not null.
`own-slot-of(Slot, Frame)`	The predicate is true if the slot is an own slot of the frame.
`positive(Number)`	The predicate is true if the number is a positive number.
`prefix-of(String, String)`	The predicate is true if the first parameter is a prefix of the second parameter.
`prime(Integer)`	The predicate is true if the integer is a prime integer.
`slot-at-class-is-boolean-valued(Slot, Class)`	The predicate is true if the slot belonging to the class is of value type boolean.
`slot-at-class-is-class-valued(Slot, Class)`	The predicate is true if the slot belonging to the class is of value type class.
`slot-at-class-is-float-valued(Slot, Class)`	The predicate is true if the slot belonging to the class is of value type float.
`slot-at-class-is-frame-valued(Slot, Class)`	The predicate is true if the slot belonging to the class is of value type frame.
`slot-at-class-is-instance-valued(Slot, Class)`	The predicate is true if the slot belonging to the class is of value type instance.
`slot-at-class-is-integer-valued(Slot, Class)`	The predicate is true if the slot belonging to the class is of value type integer.
`slot-at-class-is-primitive-valued(Slot, Class)`	The predicate is true if the slot belonging to the class is one of the primitive types, including boolean, string, integer, float, and symbol.
`slot-at-class-is-single-valued(Slot, Class)`	The predicate is true if the slot belonging to the class allows only single value.
`slot-at-class-is-string-valued(Slot, Class)`	The predicate is true if the slot belonging to the class is of value type string.
`slot-at-class-is-symbol-valued(Slot, Class)`	The predicate is true if the slot belonging to the class is of value type symbol.

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