Words with repeating symbols in prolog v5.2 - prolog

Question

I need to write prolog predicate that reads file and creates a list of words with repeating symbols. For example from text:
A dog and an apple and a pipe.
the result should be:
['apple', 'pipe']
I wrote this:
domains
file_ = f
s=string
c=char
i=integer
list=s*
list1=c*
predicates
str_a_list(s,list)
readfile(s,s)
example(s)
write_symbols(list1)
search(list1,list1,list1)
check(list)
str_list(s,list1)
search1(list1,c,i,i)
clauses
readfile(S,N):-existfile(N),!,
openread(F,N),
readdevice(F),file_str(N,S).
str_a_list("",_):-!.
str_a_list(" ",_):-!.
str_a_list(S,[H|T]):-fronttoken(S,H,S1),
str_a_list(S1,T).
search1([],_,I,I):-!.
search1([H|T],H,I,M):-I1=I+1,search1(T,H,I1,M).
search1([H|T],X,I,M):-H<>X,search1(T,X,I,M).
search([],_,_):-!.
search([H|T1],L,L0):-search1(L,H,0,M),M>=2,write_symbols(L0).
search([_|T],L,L0):-search(T,L,L0).
write_symbols([]):-write(" "),!.
write_symbols([H|T]):-write(H),write_symbols(T).
str_list("",[]).
str_list(S,[H|T]):- frontchar(S,H,S1),str_list(S1,T).
check([]):-!.
check([H|T]):-str_list(H,L),search(L,L,L),check(T).
example(Y):-readfile(S,Y),str_a_list(S,L),check(L).
goal
write("Enter file name: "),
readln(Y),example(Y).
It's giving me this error:
This flow pattern doesn't exist openread(o,i)
on line:
openread(F,N)

Answer 1

I tried computing this prolog task, maybe you may find something useful in my solution that may help you with yours. I've written my code using basic prolog:
First: The first predicate separates the sentence into words. I have used the built-in function split_string.Example: "The dog" will become "The","dog".
g(B):-
split_string(B,' ','', L),
d(L).
Second: In the second predicate, we split each word into a separate list of characters. Example: "dog" will become ["d","o","g"].
stringsplit(A,L1):-
atom_chars(A, L1).
Third: Then check each list if it contains doubles. the base case predicate tell to stop when get empty brackets. The checkdouble second predicate checks if a character is in the remaining list (using member). If yes then load the character in List R. Else, don't load the character in R.
checkdouble([],[]):-!.
checkdouble([H|T],[H|R]):-
member(H,T),
checkdouble(T,R).
checkdouble([],[]).
checkdouble([H|T],List):-
\+member(H,T),
checkdouble(T,List).
Fourth: By this point you will have a number of list: empty and those containing duplicates from each word. Example: For [bat] [apple] [polo] we will get [][p][o].
So now we use a predicate that simply prints the list of words that have doubles ignoring those words with no doubles i.e [].
s(_,B):-
B=[].
s(D,B):-
B\=[],
write(D).
Finally: Putting the code together:
g(B):-
split_string(B,' ','', L),
d(L).
d([]).
d([H|T]):-
stringsplit(H,K),
checkdouble(K,R),
s([H],R),
d(T).
s(_,B):-
B=[].
s(D,B):-
B\=[],
write(D).
checkdouble([],[]):-!.
checkdouble([H|T],[H|R]):-
member(H,T),
checkdouble(T,R).
checkdouble([],[]).
checkdouble([H|T],List):-
\+member(H,T),
checkdouble(T,List).
stringsplit(A,L1):-
atom_chars(A, L1).
Example:
?-g("A dog and an apple and a pipe").
OUTPUT:
[apple][pipe]
1true
false
?-g("Two funny little red apples fell from a tree one day").
OUTPUT:
[funny][little][apples][fell][tree]
1true
false
?-g("On a hill upon the grass there sits a squirrel in the chill").
OUTPUT:
[hill][grass][there][sits][squirrel][chill]
1true
false