update(+Key, +Struct, +Old, -New)

Key

Key argument position (non-negative integer, or list of those)

Struct

Structure

Old

Strictly ordered list of structures

New

Strictly ordered list of structures, or variable

Description

Inserts the compound term Struct into the ordered list Old, giving New. The lists are both in strictly ascending order (according to their elements' Key'th argument), i.e. without duplicates. If Old already contains an element with the same key as Struct, then Struct replaces this existing element. Otherwise, Struct is inserted at the correct position to maintain the list order.

The list New is either of the same length as Old, or one longer.

Modes and Determinism

• update(+, +, +, -) is det

Exceptions

(4) instantiation fault

Arguments are insufficiently instantiated

(5) type error

Some argument or its components are of the wrong type

(6) out of range

Some structure does not have a Key'th argument

Examples

    ?- update(1, f(2,b), [f(1,a),f(3,c)], New).
    New = [f(1,a), f(2,b), f(3,c)]
    Yes (0.00s cpu)

    ?- update(1, f(2,new), [f(1,a),f(2,b),f(3,c)], New).
    New = [f(1,a), f(2,new), f(3,c)]
    Yes (0.00s cpu)

See Also