Prolog/Introduction/Answers

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We'll use the following database, to represent a section of this family tree.

man(sirius_black). man(regulus_black). man(orion_black). man(cygnus_black). man(pollux_black).

woman(bellatrix_black). woman(andromeda_black). woman(narcissa_black). woman(walburga_black). woman(druella_roisier). woman(irma_crabbe).

parent(orion_black, sirius_black). parent(walburga_black, sirius_black). parent(orion_black, regulus_black). parent(walburga_black, regulus_black).

parent(cygnus_black, bellatrix_black). parent(druella_roisier, bellatrix_black). parent(cygnus_black, andromeda_black). parent(druella_roisier, andromeda_black). parent(cygnus_black, narcissa_black). parent(druella_roisier, narcissa_black).

parent(pollux_black, walburga_black). parent(irma_crabbe, walburga_black). parent(pollux_black, cygnus_black). parent(irma_crabbe, cygnus_black).

1. List the women in the database ?- woman(Woman). Woman = bellatrix_black ; Woman = andromeda_black ; Woman = narcissa_black ; Woman = walburga_black ; Woman = druella_rosier ; Woman = irma_crabbe.

2. List the children in the database ?- parent(_, Child). Child = sirius_black ; Child = sirius_black ; Child = regulus_black ; ...

3. List all combinations of a father and his son. ?- parent(Father, Son), man(Father), man(Son). Father = orion_black, Son = sirius_black ; Father = orion_black, Son = regulus_black ; Father = pollux_black, Son = cygnus_black ; fail.

4. which women have both a father and a son in the database? ?- woman(Woman), parent(Father, Woman), parent(Woman, Son), man(Father), man(Son).

Woman = walburga_black, Father = pollux_black, Son = sirius_black;

Woman = walburga_black, Father = pollux_black, Son = regulus_black ;

fail.

5. (Extra question) Can you think of a way to display those women that do not have a father listed in the database? Can you describe what you would need to write such a query??

You need to use negation.

Rules to put inside db:

hasFather(Somebody):- parent(Father,Somebody), man(Father). womenWithNoFather(Woman) :- woman(Woman), \+ hasFather(Woman).

Query: ?- womenWithNoFather(Woman).

Woman = druella_roisier ; Woman = irma_crabbe ;

fail.