Re: [boost] Unicode: what kind of binary compatibility do we want?

Subject: Re: [boost] Unicode: what kind of binary compatibility do we want?
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2009-06-03 09:08:31

Mathias Gaunard wrote
On Tuesday, June 02, 2009 12:22 PM
> Stewart, Robert wrote:
>
> > I don't know the implications of this, but I generally
> > dislike the idea of a silent fallback.  I'd prefer to see two
> > interfaces: one throws an exception on out of range values
> > and one that accepts a default value to return in those cases.
>
> If the character has some new property value it means it had
> the default property value (which isn't really a property, it's
> more like a "other" or "any") in the previous versions, I'm
> fairly sure Unicode guarantees this.

It is important to be positive about this.  If the default *is* appropriate for a new property value in all cases, then your approach is reasonable.

> > It might be useful to determine compatibility when the
> library starts, perhaps via an initialization call, and use
> the Strategy Pattern to determine the implementation.  (When
> compatible, a property's accesses are unchecked.  When
> incompatible, the property's accesses are checked.)
>
> That would mean virtual function call overhead, which should
> be higher than a simple branching in an inlined function.

Until you satisfy the requirements, performance isn't important.  If your default handling approach is reasonable, then you must measure performance in real use cases.  Until those points are addressed, you don't know the implications of using virtual calls.  Don't dismiss them out of hand.

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer, Core Software      using std::disclaimer;
Susquehanna International Group, LLP  http://www.sig.com

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