Re: removing items from a nested list.


Bart Demoen wrote:
wooks wrote:
I am translating the Little Schemer into Prolog as a means of learning
the language.

rember*/3 produces a list with all occurrences of the 1st term removed
from the nested list provided in the 2nd tem.

rember*(Item,[],[]).
rember*(Item,[[Head]|Tail], Result) :-
rember*(Item,Head,Result),
rember*(Item,Tail,Result).
rember*(Item, [Item|Tail], Result) :-
rember*(Item,Tail,Result).
rember*(Item,[Head|Tail], Result) :-
rember*(Item,Tail,Result).

Others will help you with semantics, let me say something about syntax:

rember*(Item,[],[]).

is syntactically the same to Prolog as

*(rember, (Item,[],[])).

so the predicate you are really defining here is */2; it is allowed, but
perhaps not what you want. You can check this by the query (and result):

?- *(X,Y).

X = rember
Y = _G245, [], []

It might be good to write

'rember*'(Item,[],[]).

or get rid of the * completely.


Cheers

Bart Demoen

I have got rid of the * . Have also experimented wit the 2nd rule. Same
result.

.

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