Prolog/Introduction/Answers
< Prolog | Introduction
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editWe'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.