问题
I am new to prolog and would appreciate any help on the following question:
I need to write a program that accepts two lists and appends the second to first and displays this new list and its length. I know that prolog might have some built in functions to make this all easier...but I do not want to use those.
eg: newlist([a,b,c],[d,e,f],L3,Le). would return L3=[a,b,c,d,e,f] and Le=6
Here is what I have so far:
newlist([],List,List,0)
newlist([Element|List1],List2,[Element|List3],L) :- newlist(List1,List2,List3, LT), L is LT + 1.
This does the appending correctly but I can only get the length of the first list instead of the combined list. Is there a way for me to add the second list's length to the first to get the combined list length?
Thanks, and sorry if this question is rather easy...I am new.
回答1:
Is there a way for me to add the second list's length to the first to get the combined list length?
You should replace:
newlist([],List,List,0).
with:
newlist([],List,List,X):-length(List,X).
来源：https://stackoverflow.com/questions/15018398/prolog-combining-two-lists