C#•3y ago

Replace element in immutable array matching predicate [Answered]

Got a simple issue, I want to replace an element in an ImmutableArray<T> which matches a predicate with another item. Is there some handy Linq method which could do this easily or am I just gonna have to write my own?

17 Replies

Doombox•3y ago

forgive the ignorance, but doesn't that kind of defeat the purpose of an immutable array?

ThinkerOP•3y ago

I say "replace an item" when I really mean "return a new immutable array with the item replaced"

Doombox•3y ago

I guess you'd just have to create your own ToImmutableArray() extension other than that just use regular LINQ to exclude the item then pass it into a new ImmutableArray.Create<T>(immutable.Where(x => x != y).ToArray()) the extension method would basically be the same deal oh you want to replace that specific item, not remove it, i can't read then yeah LINQ doesn't have a replace out of the box,, so you'd have to write that too

MODiX•3y ago

thinker227#5176

REPL Result: Success

record Person(string Name, int Age);
static IEnumerable<T> ReplaceElement<T>(this IEnumerable<T> source, Func<T, bool> predicate, T item)
{
    foreach (var x in source)
    {
        if (predicate(x)) yield return item;
        else yield return x;
    }
}

var people = new Person[] {new("Rick Astley", 53), new("Michael Stevens", 36)};
people.ReplaceElement(p => p.Age > 50, new("Joe Biden", 79))

record Person(string Name, int Age);
static IEnumerable<T> ReplaceElement<T>(this IEnumerable<T> source, Func<T, bool> predicate, T item)
{
    foreach (var x in source)
    {
        if (predicate(x)) yield return item;
        else yield return x;
    }
}

var people = new Person[] {new("Rick Astley", 53), new("Michael Stevens", 36)};
people.ReplaceElement(p => p.Age > 50, new("Joe Biden", 79))

Result: <ReplaceElement>d__2<Person>

[
  {
    "name": "Joe Biden",
    "age": 79
  },
  {
    "name": "Michael Stevens",
    "age": 36
  }
]

[
  {
    "name": "Joe Biden",
    "age": 79
  },
  {
    "name": "Michael Stevens",
    "age": 36
  }
]

Compile: 724.712ms | Execution: 174.702ms | React with ❌ to remove this embed.

ThinkerOP•3y ago

yeah that works

Doombox•3y ago

implement ToImmutableArray() and ReplaceElement and you're golden

ThinkerOP•3y ago

ToImmutableArray() already exists catsip

Doombox•3y ago

does it? then even less work sunglas

implemented my own immutable collections if I needed them, first time I'm hearing of an immutable collections namespace and nuget package

MODiX•3y ago

thinker227#5176

REPL Result: Success

using System.Collections.Immutable;
new[] {1,2,3,4,5}.ToImmutableArray()

using System.Collections.Immutable;
new[] {1,2,3,4,5}.ToImmutableArray()

Result: ImmutableArray<int>

[
  1,
  2,
  3,
  4,
  5
]

[
  1,
  2,
  3,
  4,
  5
]

Compile: 470.805ms | Execution: 41.198ms | React with ❌ to remove this embed.

Doombox•3y ago

feel like a bit of a catclown

now

ThinkerOP•3y ago

It's actually just part of the standard library now. I use ImmutableArray<T> pretty often since it's really useful (and optimized).

Doombox•3y ago

ah, I haven't needed one in quite a while, so probably not that much of a clown

ThinkerOP•3y ago

Nah, depends a lot on what you're doing

Doombox•3y ago

I think I needed one a couple years ago and literally just copy pasted an existing implementation I had so if it was around then I didn't even check

ThinkerOP•3y ago

If you're a masochist like me and really like functional patterns then immutability is a necessity catsip

Doombox•3y ago

mostly do immutability through exposing IReadOnly collections really but that's only technically immutable well I guess so are the immutable collections if you try hard enough

Accord•3y ago

✅ This post has been marked as answered!

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Replace element in immutable array matching predicate [Answered]

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