Swift: Not quite there, but too far gone too

Re:Swift: Not quite there, but too far gone too by cosn on Wednesday June 04, 2014 @03:37PM (#7847640)

"Immutability has a slightly different meaning for arrays, however. You are still not allowed to perform any action that has the potential to change the size of an immutable array, but you are allowed to set a new value for an existing index in the array. This enables Swift’s Array type to provide optimal performance for array operations when the size of an array is fixed."

https://developer.apple.com/library/prerelease/ios/documenta...

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Re:Swift: Not quite there, but too far gone too by danudey on Wednesday June 04, 2014 @05:03PM (#7848292)

So immutability is a code safety feature, except in the case of arrays, where it's a performance optimization. That seems counterintuitive.

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Re:Swift: Not quite there, but too far gone too by josephlord on Wednesday June 04, 2014 @06:08PM (#7848713)

Thanks. I think it sounds like a bad decision, it can be compile time checked so won't cause performance issues. I wonder what the cost is in the mutable case for the fact that the length can vary.

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