I have a question : I know merge two list in SML but i can not do the total number of elements of the first list and the second list is less than n, append them fully and return the resulting list appended with 0’s, totaling n elements.
Sample :
f2([1,4,5],[3,6],7);
val it = [1,4,5,3,6,0,0] : int list // 7 elements
Thank you in advance..
Get the length of the two lists with LIST.length and compare the sum with the third argument.
I am not sure what to do if this sum is larger than the third argument but you get the idea.
if sum < n then list1 # list2 # 0.....
Related
I am using cp_model to solve a problem very similar to the multiple-knapsack problem (https://developers.google.com/optimization/bin/multiple_knapsack). Just like in the example code, I use some boolean variables to encode membership:
# Variables
# x[i, j] = 1 if item i is packed in bin j.
x = {}
for i in data['items']:
for j in data['bins']:
x[(i, j)] = solver.IntVar(0, 1, 'x_%i_%i' % (i, j))
What is specific to my problem is that there are a large number of fungible items. There may be 5 items of type 1 and 10 items of type 2. Any item is exchangeable with items of the same type. Using the boolean variables to encode the problem implicitly assumes that the order of the assignment for the same type of items matter. But in fact, the order does not matter and only takes up unnecessary computation time.
I am wondering if there is any way to design the model so that it accurately expresses that we are allocating from fungible pools of items to save computation.
Instead of creating 5 Boolean variables for 5 items of type 'i' in bin 'b', just create an integer variable 'count' from 0 to 5 of items 'i' in bin 'b'. Then sum over b (count[i][b]) == #item b
i want this answer
if Input list is >> List( List("A","B"),List("A","C"),List("B","C"),List("B","D"))
Output should be >> List(List("A", "B","C"),List("B","C","D"))
i think it should be done as following>> all indices having first element same are grouped e.g if first element is "A" then group will be ("A","B","B","C").distinct = ("A","B","C")
Say we have a kdb list
L1:(1 2 3 4 5)
Apply condition
L1 < 3
And how can I retrieve result in another list (1 2)
You can use the where keyword for this:
q)l1 where l1<3
1 2
Applying l1<3 will return a list of booleans 11000b. Using where on this list will return the index of every 1b
q)where 11000b
0 1
Then indexing back into the original list will return the result in another list.
I am trying something (in netlogo), but it is not working. I want a value of a position from a list of numbers. And I want to use the number that comes out of it to retrieve a name from a list of names.
So if I have a list like [1 2 3 4] en a list with ["chicken" "duck" "monkey" "dog"]
I want my number 2 to correspond with "duck".
So far, my zq is a list of numbers and my usedstrategies is a list of names.
let m precision (max zq) 1
let l position m zq
let p (position l zq) usedstrategies
But when I try this the result will be false, because l is not part of usedstrategies.
Ideas?
You need the item primitive to select from the list after matching on the other list. I am not sure what the precision line is for. However, here is a self contained piece of code that I think demonstrates what you want to do. Note that NetLogo counts positions from 0, not 1. I also used arbitrary numbers in the list so you don't get confused between the number in the list and its position.
to testme
let usedstrategies (list "chicken" "duck" "monkey" "dog")
let zq (list 5 6 7 8)
let strategynum position 7 zq
let thisstrategy item strategynum usedstrategies
type "Selected strategy number " type strategynum
type " which is " print thisstrategy
end
Jen's solution is perfectly fine, but I think this could also be a good use case for the table extension. Here is an example:
extensions [table]
to demo
let usedstrategies ["chicken" "duck" "monkey" "dog"]
let zq [5 6 7 8]
let strategies table:from-list (map list zq usedstrategies)
; get item corresponding with number 7:
print table:get strategies 7
end
A "table", here, is a data structure where a set of keys are associated with values. Here, your numbers are the keys and the strategies are the values.
If you try to get an item for which there is no key in the table (e.g., table:get strategies 9), you'll get the following error:
Extension exception: No value for 9 in table.
Here is a bit more detail about how the code works.
To construct the table, we use the table:from-list reporter, which takes a list of lists as input and gives you back a table where the first item of each sublist is used as a key and the second item is used as a value.
To construct our list of lists, we use the map primitive. This part is a bit more tricky to understand. The map primitive needs two kind of inputs: one or more lists, and a reporter to be applied to elements of these lists. The reporter comes first, and the whole expression needs to be inside parentheses:
(map list zq usedstrategies)
This expression "zips" our two lists together: it takes the first element of zq and the first element of usedstrategies, passes them to the list reporter, which constructs a list with these two elements, and adds that result to a new list. It then takes the second element of zq and the second element of usedstrategies and does the same thing with them, until we have a list that looks like:
[[5 "chicken"] [6 "duck"] [7 "monkey"] [8 "dog"]]
Note that the zipping expression could also have be written:
(map [ [a b] -> list a b ] zq usedstrategies)
...but it's a more roundabout way to do it. The list reporter by itself is already what we want; there is no need to construct a separate anonymous reporter that does the same thing.
If you have a list and another list with indices (limited number) in of the first list in ascending order.
How can you get a sum of elements in the first list between consecutive indices in the second list.
e.g:
list1: til 100;
idx: (1 20 50 70 100);
How can we get a list with sum of elements of list from elements 1:20, 20:50, 50:70, 70:100?
The obvious approach would be to use # and _ on elements of the idx but can we do that iteratively somehow without using first, first 1_idx etc.
Something like this would work:
q)sum each idx cut list1
190 1035 1190 2535 0
cut operates by cutting the second argument at the indices given in the first. Hence why you see the 0 at the end of the result, as it's cutting at the 100th element.