schwa/approximateequality

``ApproximateEquality`` protocol

For numeric types this uses `isApproximatelyEqual` from Swift Numerics.

``DeriveApproximateEquality`` macro.

Annotate your types with `DeriveApproximateEquality to automatically conform to ApproximateEquality` and derive an implementation.

`DeriveApproximateEquality` Example

import ApproximateEquality
import ApproximateEqualityMacros
import CoreGraphics

@DeriveApproximateEquality
public struct MyType {
    var x: Double
    var y: CGPoint
    @ApproximateEqualityIgnored
    var z: Double
    var w: Float
}

let thing1 = MyType(x: 10, y: CGPoint(x: 20, y: 0), z: 30, w: 0)
let thing2 = MyType(x: 10, y: CGPoint(x: 20, y: 0), z: 40, w: 0)
let error = 0.000_001
let thing3 = MyType(x: 10 + error, y: CGPoint(x: 20, y: 0), z: 40, w: 0)

print(thing1.isApproximatelyEqual(to: thing2, absoluteTolerance: 0.0001))      // true
print(thing1.isApproximatelyEqual(to: thing3, absoluteTolerance: 0.0001))      // true
print(thing1.isApproximatelyEqual(to: thing3, absoluteTolerance: 0.000_000_1)) // false

Expanding the `@DeriveApproximateEquality` macro generates an extension:

extension MyType: ApproximateEquality {
    public func isApproximatelyEqual(to other: Self, absoluteTolerance: Double.Magnitude) -> Bool {
        x.isApproximatelyEqual(to: other.x, absoluteTolerance: Double.Magnitude(absoluteTolerance))
        && y.isApproximatelyEqual(to: other.y, absoluteTolerance: CGPoint.Magnitude(absoluteTolerance))
        && w.isApproximatelyEqual(to: other.w, absoluteTolerance: Float.Magnitude(absoluteTolerance))
    }
}

Note that the property prefixed with `@ApproximateEqualityIgnored` is used in the implementation.

License

MIT.

Portions of thise code are from the Apple-Numerics (<https://github.com/apple/swift-numerics>) project and are licensed under the Apache License

TODO

• [ ]: Test against more complex types.
• [X]: Pass through absolute tolerance, norm etc.
• [X]: Handle the casting to Double in `DeriveApproximateEquality`

Package Metadata

Repository: schwa/approximateequality

Default branch: main

README: README.md