logo
Tags down

shadow

How to work with mutable lists in F#?


By : chuck_d
Date : October 18 2020, 01:08 AM
I wish this helpful for you In F# the type List<'t> is the immutable F# list. It is not the same as System.Collections.Generic.List, which is what is described in the docs you linked.
To access the latter, either open the System.Collections.Generic namespace (but beware: this will shadow the regular F# list) or refer to it by its F# alias, ResizeArray<'t>, which also better expresses its true nature.
code :
let rec getSubLists (len : int) (list : ResizeArray<int>) : ResizeArray<ResizeArray<int>> =
  let result = new ResizeArray<ResizeArray<int>>()
  let current = new ResizeArray<int>()

  let rec findSubLists (len : int) (superSet : ResizeArray<int>) (current : ResizeArray<int>) (soln : ResizeArray<ResizeArray<int>>) (idx : int) : unit =
    if current.Count = len then soln.Insert(len - 1, current)
    elif idx = superSet.Count then
      let x = superSet.[idx] 
      current.Insert(len, x)
      findSubLists len superSet current soln (idx + 1)
      current.RemoveAt(x)
      findSubLists len superSet current soln (idx + 1)
    else ()

  findSubLists len list current result 0
  result


Share : facebook icon twitter icon

how does equating lists work? -basic concepts of mutable


By : Koala R. Robert
Date : March 29 2020, 07:55 AM
Hope that helps why in the following case list2 is not [3,5] ? , Python variable names point at objects.
code :
list2=list1
list1[0]=2
list1=[3,5,7]

folding with mutable.Map and mutable.Set does not work when using Set.add


By : rbx
Date : March 29 2020, 07:55 AM
Hope this helps .withDefaultValue does not add the value to Map. Use .getOrElseUpdate(strVal, Set.empty).add(intVal) instead.

Append two mutable lists


By : Najun.Nazar
Date : March 29 2020, 07:55 AM
it helps some times See the documentation on mappend!

Are Lists mutable?


By : Eliott Ham
Date : March 29 2020, 07:55 AM
This might help you The + operator is not a mutator, it returns a new list containing the concatenation of the input lists.
On the other hand, the += operator is a mutator. So if you do:

Are Python Lists mutable?


By : Amin Mpf
Date : March 29 2020, 07:55 AM
it helps some times You created a new list object and bound it to the same name, x. You never mutated the existing list object bound to x at the start.
Names in Python are just references. Assignment is binding a name to an object. When you assign to x again, you are pointing that reference to a different object. In your code, you simply created a whole new list object, then rebound x to that new object.
shadow
Privacy Policy - Terms - Contact Us © soohba.com