recursion - Searching for a value in a list with Prolog -



recursion - Searching for a value in a list with Prolog -

i'm writing recursive function in prolog check if course of study (crs) in semester (sem, list) has pre requisite course of study met in prior (a list). there 2 examples of course of study in sec block of code. when runs fails csse1001 (which has no prerequisite), when should homecoming true has search nothing. missing?

checksem(prior,[]). checksem(prior,sem):- [crs|tail] = sem, member(pre(crs,list),prior), checksem(prior,tail).

course:

parta(comp3506). lvl3(comp3506). s1(comp3506). pre(comp3506,[csse2002]). parta(csse1001). lvl1(csse1001). s1(csse1001). pre(csse1001,[]).

you did not give illustration query checksem/2 guess first argument prior list of courses. think should check if name of course of study fellow member in prior , not pre(crs, list). second, have list of prerequisites , not one, should check of them members in prior.

checksem(_,[]). checksem(prior,[crs|tail]):- pre(crs, list), \+ (member(prereq, list), \+ member(prereq, prior)), checksem(prior,tail).

this goal \+ (member(prereq, list), \+ member(prereq, prior)) satisfied if there exists no course of study prereq fellow member of list , it's not fellow member of prior.

list recursion prolog member

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