separate_by_key(+Key, +Value, +All, -Matches, -Others)

Key

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

Value

A term

All

List of structures

Matches

Variable, or list of structures

Others

Variable, or list of structures

Description

The list All is separated into two lists Matches and Others, such that Matches contains the elements whose Key argument is identical (in the sense of ==/2) to Value, and Others is a list with those matching elements deleted. The original list does not have to be ordered. The element order in the result lists corresponds to the order in the original list.

Modes and Determinism

• separate_by_key(+, +, +, -, -) 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

    ?- separate_by_key(1, b, [f(a,1),f(b,2),f(c,3),f(b,4)], Bs, Ns).
    Bs = [f(b,2), f(b,4)]
    Ns = [f(a,1), f(c,3)]
    Yes (0.00s cpu)

See Also