%%
%% lists.pl
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%% Author(s):
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%% CS 60 Hw 8, extra credit
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%%


% some "nice" prolog settings...  see assignment 

:- set_prolog_flag( prompt_alternatives_on, groundness ).
:- set_prolog_flag(toplevel_print_options, [quoted(true), 
     portray(true), attributes(portray), max_depth(999), priority(699)]).


%% a couple of example predicates that might be helpful...

%
% member( E, L ) should be true if E is a top-level member of the list L
% member should work when E is a variable or bound; L should be bound
%
member( E, [E|_] ).
member( E, [_|R] ) :- member( E, R ).


%
% reverse( L, Rev ) should be true if Rev is the reverse of the list L
% reverse should work when Rev is a variable or bound; L should be bound
%
reverse( [], [] ).   % base case!
reverse( [F|R], Rev ) :- reverse( R, Tmp ), append( Tmp, [F], Rev ).



%% Here are commented-out placeholders for the two extra-credit predicates.
%%
%% Their descriptions are in the assignment itself.
%%
%% Be sure to comment each predicate you write!



%% removeOne( E, L, NewL )



%% find( Pattern, Target, Index )