Re: [TCLCORE] Tcl 9 Wart Removal List, Rev. 4 [bytelength]

[Joe E. <jen...@fl...>]

Kieran Elby wrote:
> [...]
> Incidentally, [string bytelength $v] is not quite the same as
> [string length [encoding convertto utf-8 $v]] - consider this example:
> [...]
> One use-case I've encountered for "string bytelength" is to help
> truncate a string so that it's UTF-8 encoding will fit in a database
> column whose length is specified in bytes.

Which, as you point out above, is incorrect;
[string bytelength $v] is not always the same as
the number of bytes in the UTF-8 encoding of $v.

> Another use-case is estimating the size of a Tcl value in memory - but
> perhaps an info subcommand or a special debugging command for this
> purpose would be more appropriate?

This too will give inaccurate results.  The amount of memory
allocated for the string rep of a value is generally not
the same as its [string bytelength] either.  (Tcl will
overallocate the string buffer under certain circumstances
to help ensure amortized O(n) time for [append]).

I think this just underscores my point.  In every use case
I've seen, [string bytelength] is nothing more than a
cheap way to get the answer to the wrong question :-)


--Joe English

  jen...@fl...