Christian Tismer wrote:
And the key assumption for sorting things is that the things are sortable, which means there exists and order on the basic set. Which again suggests that list elements usually have something in common.
To me it suggests that some lists are sortable and others are not... There's one aspect about this discussion that I haven't seen mentioned yet: syntax. I think the suggested usages of lists vs. tuples has more to do with list vs. tuple _syntax_, and less with mutability. From this perspective it is natural that tuples support a different set of methods than lists. However, mutable vs. immutable has it's uses also, and from _that_ perspective it is far less understandable that tuples lack certain methods. FWIW, I quite like the way how the core classes in Cocoa/NextStep are designed. For each container-ish object there's a mutable an immutable variant, where the mutable variant is usually a subclass of the immutable one. Examples: NSString -> NSMutableString NSData -> NSMutableData NSArray -> NSMutableArray NSDictionary -> NSMutableDictionary (But then again, Objective-C doesn't have syntax support for lists _or_ tuples...) Just