PLOGHELP BAGOF              Jonathan Laventhol, Thursday 22nd March 1984
                                Revised by Kathryn Seifert  October 1986

Produces a bag of patterns which will satisfy a given goal

    ?- bagof(Pattern, Goal, Bag).

Keywords: goal, goal satisfaction


This predicate produces a Bag of Patterns such that Goal is satisfiable.
A "bag" is an unordered set which may contain duplicate elements.
'bagof' is like 'setof' except that it does not order the elements of
Bag and allows duplicates.

In a query of the form:

    ?- bagof(Ma, parents(Pa, Ma, Child), B).

'bagof' will treat the meaning of this query as "B is the bag of all Mas
such that Pa and Ma are the father and mother of Child for some SPECIFIC
Pa and Child".

For example, given the database of facts:

    parents(frances, richard, kathy).
    parents(elsie, mel, jon).
    parents(joanne, kenny, frank).

we can call 'bagof' as above with the following results:

    ?- bagof(Ma, parents(Ma, Pa, Child), B).
    Ma = _1
    Pa = kenny
    Child = frank
    B = [joanne] ? ;

    Ma = _1
    Pa = mel
    Child = jon
    B = [elsie] ? ;

    Ma = _1
    Pa = richard
    Child = kathy
    B = [frances] ? ;

    no

Compare with * FAST_BAGOF, * SETOF, and * FAST_SETOF.

-- RELATED DOCUMENTATION ----------------------------------------------

PLOGHELP * FAST_BAGOF
 Fast version of 'bagof'

PLOGHELP * SETOF
 Produces a set of patterns which will satisfy a given goal

PLOGHELP * FAST_SETOF
 Fast version of 'setof'

PLOGHELP * FINDALL
 Library program to find all the terms which satisfy a given predicate