🚀 Add remove(where:) for Set and Dictionary 🎯

[krishpranav]

This PR introduces a powerful and highly-requested feature: the remove(where:) method for both Set and Dictionary. This enhancement allows developers to efficiently remove elements from these collections based on a condition, leveraging Swift's expressive closures.

Motivation

🔍 Current implementations make it challenging to remove elements efficiently from Set and Dictionary based on conditions. Developers either need to iterate over snapshots (causing unnecessary copying) or collect items in a separate collection for removal. This PR addresses these inefficiencies by providing a native, performant solution.

What's New?

1️⃣ Set.remove(where:): Removes the first element satisfying the condition, if any.
2️⃣ Dictionary.remove(where:): Removes all key-value pairs satisfying the condition.
3️⃣ Comprehensive unit tests included to ensure robustness.

Example Usage

For Set:

var numbers: Set = [1, 2, 3, 4, 5]

// Remove the first even number
if let removedElement = numbers.remove(where: { $0 % 2 == 0 }) {
    print("Removed element: \(removedElement)")  // Output: Removed element: 2
}

print(numbers)  // Output: [1, 3, 4, 5]

For Dictionary:

var people = ["Alice": 25, "Bob": 30, "Charlie": 35]

// Remove people younger than 30
people.remove(where: { $0.value < 30 })

print(people)  // Output: ["Bob": 30, "Charlie": 35]

Implementation Details

• Introduced remove(where:) as mutating functions in Set and Dictionary.
• Optimized for performance, directly modifying the underlying storage.
• Added extensive tests in test/stdlib/Set.swift and test/stdlib/Dictionary.swift.

Why This Matters

💡 This feature simplifies common use cases, improving Swift's ergonomics and efficiency for developers. It's an essential step toward making Swift's standard library more versatile and user-friendly.

References

• Issue: #78364
• Proposal: [Swift Evolution Proposal]
• Pull Request: (✨ Add remove(where:) Method to Set and Dictionary for Seamless Element Removal ✨ swift#78600)

[stephentyrone]

proposal numbers are assigned by the review manager when review starts. The text (and filename) should be 0000- or NNNN- for now to avoid confusion.

[krishpranav]

pushed it.

[stephentyrone]

The proposal seems mostly OK, but I have some high-level questions about this proposed API. First off, it really should be something like removeFirst(where:)--remove(where:) makes me think that it's going to remove every element that satisfies the predicate (i.e. the inverse of filter). But that's also kind of weird, because Sets and Dictionaries do not have a semantically meaningful notion of "first"--there's an ordering, but it's more of a necessary inconvenience than a meaningful part of the API (and it's unstable run to run).

Can you give some examples of the real problems that you want to use this API to solve? I have some ideas about how I would use it, but I'd like to see some others and think about what other shapes this API might take that aren't as fundamentally dependent on the ordering of Set or Dictionary elements.

[krishpranav]

@stephentyrone kindly give me sometime, will get back to you.

[stephentyrone]

For anyone following along, I would write this:

removedElement = numbers.first(where: { $0.isMultiple(of: 2) }).map {
  numbers.remove($0)!
}