[swift-users] Why does the withUnsafeMutableBufferPointer closure take an inout parameter?

[Martin R]

I wonder why the closure in the Array method

    mutating func withUnsafeMutableBufferPointer<R>(_ body: (inout UnsafeMutableBufferPointer<Array.Element>) throws -> R) rethrows -> R

takes an _inout_ parameter. The closure is called with a pointer to the contiguous array storage, and I fail to imagine an example where it makes sense to assign a new value to the parameter.

Any insights are welcome!

Regards, Martin