Re: [TCLCORE] Agressive shimmering

[Brian G. <bri...@me...>]

On Jan 17, 2013, at 10:57 AM, Porter, Don wrote:

> 
> Remember that [string length] returns the number of characters in
> the string.  That information is not stored anywhere in the Tcl_Obj struct.
> 
> (objPtr->length is in bytes, not chars)
> 
> The shimmer happens so that we have someplace to store the computed
> length in chars, so when it's asked for again we don't have to compute it again.
> 
> Looking at the 8.4 source code, it does the same.  You should not see any
> difference in the shimmer pattern moving from 8.4 to 8.5.
> 
> Tcl_GetCharLength() calls SetStringFromAny() which shimmers.  Don't you
> see that in your examples?

That's not my experience, comparing 8.4.14 vs 8.5.8.
And practically speaking we deal with simple ascii 99.999% of the time, iso8859-1 technically.  Also, most of the [string length] operations only care about !=0 tests.

-Brian