Hi Morten, > On Jan 9, 2017, at 2:16 AM, Morten Bek Ditlevsen via swift-corelibs-dev > <swift-corelibs-dev@swift.org> wrote: > > Hi list, > I was looking at the NSDecimal.swift to learn a bit about the implementation > of the Decimal type. > I get that a lot of the API in this type exists for compatibility reasons > with the C implementation. > > But I was wondering about how the NSDecimalCopy function differs from a > simple assignment of one Decimal value to another. > > NSDecimalCopy simply assigns each field of the struct one by one, so when > would it ever be preferable to performing a simple assignment? > > So basically my question is - is there any difference in the result of > performing: > > var a: Decimal = 1 > var b: Decimal = 2 > NSDecimalCopy(&b, &a) > > and > var a: Decimal = 1 > var b: Decimal = 2 > b = a >
I suspect that this is just due to some logic copying from the C version. I’m actually not sure what the compiler does here. It should be possible to try it out in a test app, disassemble it, and check out the result. Let us know what you find. =) - Tony > Secondly - if there is no difference in the result - is it not more > performant to assign the value directly? > > This question also raised a question about Swift internals: If you have a > pure value type (no nested reference types): Does an assignment then simply > copy a chunk of memory with the size of the struct? Or is each field > assigned/copied recursively? > > Sincerely, > /morten > _______________________________________________ > swift-corelibs-dev mailing list > swift-corelibs-dev@swift.org > https://lists.swift.org/mailman/listinfo/swift-corelibs-dev _______________________________________________ swift-corelibs-dev mailing list swift-corelibs-dev@swift.org https://lists.swift.org/mailman/listinfo/swift-corelibs-dev
