list - Having trouble with predicate in Prolog -

i trying right predicate in prolog accepts item, list, , number, , checks see if item in list number of times. example

count(7,[3,7],x). 

would return x=1.

count(7,[3,7],1). 

would return true

this have far

count_occur(a,[0|b],d). count_occur(a,[a|c],d) :- count_occur(a,c,d1), d d1+1. count_occur(a,[b|c],d) :- count_occur(a,c,d). 

i new prolog , struggling understand programming paradigm.

what trying see if first item in list matches passed-in value (a), if increment d , check again against remainder of list. how in lisp or language anyway. use help, been @ while , isn't clicking me.

i don't have prolog right test it, try that:

count_occur(a, [], 0). count_occur(a, [a|t], d):- count_occur(a, t, d1), d d1 + 1. count_occur(a, [b|t], d):- \= b, count_occur(a, t, d). 

the idea if list empty, there 0 occurrences of each element. rest same yours think correct.

the difference have added a \= b, should mean a \neq b. think otherwise accept a == b, might lead count_occur(3, [3], 0). being true. should check that.

i hope helps!