Prolog Insert list as element into another List - list

In my program my P = [0,1,2] I want to store it into another LIST, because P will keep changing in a loop so I want to store P into a LIST, so my LIST will be like below :
eg.
LIST = [[0,1,2],[3,4,5],[6,7,8]]
create_list([],[]).
create_list(G, [H|G]).
This is what I did, create_list(P,LIST). I not sure how to do it as it keep return me no. But I am pretty sure I can get different P because I am able to print them out each time P changed.

You need to create a predicate that receives the item (list in this case) you want to append to another input list, and this would give you a new list with the which has all the items of your input list plus the new item.
So, it would be something like:
create_list(Item, List, [Item|List]).
Initially the input List would be an empty list ([]), so you might call it
create_list([0,1,2], [], List1),
create_list([3,4,5], List1, List2),
create_list([6,7,8], List2, List).
This will result in List instantiated with [[0,1,2],[3,4,5],[6,7,8]]

Related

I am trying to remove the last item of each list in a list of lists

I have a data structure which is a list of lists. I want to remove the last item of each list, preferably using a filter. How would i go about doing this?
Here is an example show how to do it:
map (\xs->if null xs then xs else init xs) [[], [1..3], [4..6]]
and the result is:
[[],[1,2],[4,5]]
Note that it need to check each list in list whether is empty before remove the last item of the list, since init cannot apply to empty list.

Concatenate two list into a new list

I have two list:
lis1=[['a','b','x'],['c','d','x']]
lis2=['1','2']
and i wont a new list insert elements lis2 in lis like
[[['a','b','c','x'],['1']],
[['c','d','x'],['2']]]
What can i do?
Append method don't work for it.

difference between [] and list() in python3

I thought that [] and list() were two equal ways to create a list. But if you want a list with dictionnary keys,
var = [a_dict.keys()]
doesn't work since type(var) is [dict_keys], correct syntax is :
var = list(a_dict.keys())
I couldn't find an good explanation on this behaviour. Do you have one ?
TL;DR:
list() is the same as []
list(obj) is not the same as [obj]
a_dict.keys() is a dictionary view object, it returns an object which can be iterated to yield the keys of a_dict. So this line:
[a_dict.keys()]
is saying in python "I'm making a list with one element in it" and that one element is the dict keys iterator. It's a list literal in the syntax.
Now this line:
list(a_dict.keys())
is a call to the list builtin function. This function list attempts to iterate the argument and produce a list. It's a function call in the grammar.
The equivalent list literal (actually list comprehension) would be instead:
[key for key in a_dict.keys()]
Finally, note that dictionary objects iterate by keys anyway,
list(a_dict.keys()) would usually be written more simply as as list(a_dict) instead.
Hope this helps.
[a_dict.keys()]
This one puts a single element in the list. Just as if you were to write [1]. In this case that one element is going to be a list.
list(a_dict.keys())
The constructor accepts a sequence and will add all elements of the sequence to the container.

List Manipulation in prolog

Given a list such that [[%,A,B,C,%D,E,%],[%,F,G,%,H,I,J,%]] how do I return [[A,B,C],[D,E],[F,G],[H,I,J]]
I tried the following code:
filtertolists([],[]).
filtertolists([Head|Tail],Y):-
(Head = '%' ->
filtertolists(Tail,Y)).
I want to get the first element from the list of lists, and check whether members of the list are equal to '%' and start creating the list to be given as output, but after getting the head how do I check each element in it?
I would split the task into two tasks:
iterating over the list of lists
removing the elements of one list
My resulting sourceocde would look like this:
filtertolists([],[]).
filtertolists([List|Tail], [FilteredList|FilteredTail]):-
filterList(List, FilteredList),
filtertolists(Tail, FilteredTail).
filterList([], []).
% your filter code for one list goes here .
filterList(...).
filterList(...).

How to check and change the value of a list?

I would like to check all list values in a list and change them if necessary.
p.e.
I want to check the next lists if there are values higher or lower then the next values:
min-value = 6
max-value = 22
mylist = ['4-8','25','16-19','21-32']
if one of the list values is below the min-value or higher then the max-value, the list values must be changed to the min-value and max-value. p.e. in example, the new list must be:
mylist = ['6-8','22','16-19','21-22']
if the entire value of the list item is below the min-value or higher then the max-value the list item can be removed.
How can I check my list values and change them?
There are two approaches. In the procedural one, you iterate over the list items and modify or skip the element:
let newlist = []
for element in mylist
" Parse element.
if ! OutsideBounds(element)
call add(newlist, AdjustBounds(element))
endif
endfor
In the functional programming approach, you use the built-in map() to modify elements (i.e. adjust the bounds), but that one cannot remove elements. So just empty those elements and then do a second pass with filter() to remove them. Note that both functions modify the original lists, so use copy() if you need to keep the original.
call filter(map(mylist, 'AdjustBounds(v:val)'), '! OutsideBounds(v:val)')
I hope I don't need to tell you how to write the AdjustBounds() and OutsideBounds() functions...