On 05/10/2010 15:14, Steven Schveighoffer wrote: > On Tue, 05 Oct 2010 09:00:13 -0400, Bob Cowdery > <b...@bobcowdery.plus.com> wrote: > >> On 05/10/2010 13:45, Denis Koroskin wrote: > >>> "static this" is called a static constructor and can be used for >>> classes and modules. The code in static constructor is guarantied to >>> be called before you use that class/module, it usually happens upon >>> thread initialization. >>> >>> The other solution is better though: >>> >>> enum A_RX_FILT = [ // just works >>> "6K0": tuple(100.0, 6100.0), >>> "2K4": tuple(300.0, 2700.0), >>> "2K1": tuple(300.0, 2400.0), >>> "1K0": tuple(300.0, 1300.0), >>> "500": tuple(500.0, 1000.0), >>> "250": tuple(600.0, 850.0), >>> "100": tuple(700.0, 800.0) >>> ]; >> I'm not totally understanding that. Why can enum compute that at compile >> time and the thing which it is, an associative array cannot. Is it to do >> with where these things live. > > I'd be very wary of this solution. Recently, enum has been shown to > construct itself on every use. > > So what I think is happening is every time you use A_RX_FILT, it's > building a brand new AA (you can verify this by looking at the > disassembly). > > I'd recommend the static this solution in order to ensure you are not > accidentally killing performance by just using that AA. > > A while back, Don suggested that all literals should be considered > immutable. I agree with him, but Walter still doesn't. If all > literals are immutable, then they could be truly constructed at > compile-time. > > -Steve I'm happy with the static this solution so will leave well alone. I generally keep mutable and immutable data structures apart so I tend to agree that literals should be immutable although of course I'm not aware of the pros and cons.
bob
