On Wednesday, 28 May 2014 at 14:36:25 UTC, Chris wrote:
I use Appender to fill an array. The Appender is a class variable and is not instantiated with each function call to save instantiation. However, the return value or the function must be dup'ed, like so:Appender!(MyType[]) append; public auto doSomething() { scope (exit) { // clear append } // ... do something append ~= item; return (append.data).dup }My question is whether I save anything with Appender as a class variable here. I have to .dup the return value (+ clear the Appender). If I had a new Appender with each function call, it might be just as good.public auto doSomething() { Appender!(MyType[]) append; // .... return append.data. } Right or wrong?
When it comes to optimizations it's hard to say. Benchmarking is better than relying advice/opinions on the internet in any case.
That being said i doubt that the instantiation cost of the Appender is relevant. (Btw the appender is not a class variable! It is a struct with reference semantics). Reusing an appender is more for those cases where you want to reuse the underlying memory of the appender itself.
