Re: Alternative to bytes::length()

Sometimes, I wish for a boolean context... (It would be great for grep too.) Or maybe the character length should be stored in string variables?

I can't think of any replacement short of turning off the flag, calling length, then restoring it.

What's the problem with the current solution?

require bytes;
sub emptystr(_) {
    no warnings 'uninitialized';
    return !bytes::length($_[0]);
}
[download]

By the way,

use bytes; 
no bytes;
[download]

is equivalent to

use bytes ();
[download]

There's also similar

require bytes;
[download]

Comment on Re: Alternative to bytes::length() Select or Download Code

Replies are listed 'Best First'.
Re^2: Alternative to bytes::length() by creamygoodness (Curate) on Dec 23, 2009 at 01:38 UTC
Or maybe the character length should be stored in string variables? I think the length in characters might be cached using MAGIC -- I know some UTF-8 stuff is. What's the problem with the current solution? There was just a post to p5p from someone who wanted to terminate the bytes pragma with extreme prejudice. I wanted to mention this use case.	[reply]
Re^3: Alternative to bytes::length() by ikegami (Patriarch) on Dec 23, 2009 at 02:02 UTC
Do you have an example of this magic? That would be an argument for creating a new function, not for keeping bytes.	[reply]
Re^4: Alternative to bytes::length() by ikegami (Patriarch) on Dec 23, 2009 at 02:15 UTC
Actually, simply calling `length` on a scalar with `UTF8=1` adds the magic. `>perl -MDevel::Peek -e"Dump $_=chr(0x2660)x100; length $_; Dump $_" SV = PV(0x2379ec) at 0x1845eec REFCNT = 1 FLAGS = (POK,pPOK,UTF8) PV = 0x184c5ec "..."\0 [UTF8 "..."] CUR = 300 LEN = 304 SV = PVMG(0x18242cc) at 0x1845eec REFCNT = 1 FLAGS = (SMG,POK,pPOK,UTF8) IV = 0 NV = 0 PV = 0x184c5ec "..."\0 [UTF8 "..."] CUR = 300 LEN = 304 MAGIC = 0x1824e64 MG_VIRTUAL = &PL_vtbl_utf8 MG_TYPE = PERL_MAGIC_utf8(w) MG_LEN = 100 <---------- char length` [download] It's a pity that actions such as `chop`, appending a `UTF8=0` string, etc void the count instead of updating it. Note that `$_ eq ''` doesn't add the magic, so not only is it faster, it uses less memory.	[reply] [d/l] [select]
Re^4: Alternative to bytes::length() by creamygoodness (Curate) on Dec 23, 2009 at 02:25 UTC
Looks like you found the caching mechanism. From perlguts: `w PERL_MAGIC_utf8 vtbl_utf8 UTF-8 length+offset cac +he` [download] As for keeping `bytes`... meh, my attachment to the `bytes` pragma extended only to that use case, as the efficiency of `CORE::length()` with `SVf_UTF8` scalars is a bummer. I'm not even going to bother posting to p5p now that my concern has been addressed another way.	[reply] [d/l] [select]
Re^3: Alternative to bytes::length() by assemble (Friar) on Dec 23, 2009 at 14:15 UTC
Why would they eliminate the bytes pragma? What about those of us who aren't always manipulating character data and actually do care about the bytes themselves?	[reply]
Re^4: Alternative to bytes::length() by ikegami (Patriarch) on Dec 23, 2009 at 15:02 UTC
Strings can contain bytes. You don't have to do anything special to work with bytes. `use bytes;` has nothing to do with manipulating bytes. If you need to manipulate the internal string format to optimize or to work with some buggy XS, You want `utf8::upgrade` or `utf8::downgrade`. If you need you need to encode to UTF-8 or decode from UTF-8, You want `utf8::encode`, `Encode::encode`, `utf8::decode` or `Encode::decode`. The person probably wants to eliminate it because of that very misconception you expressed. But don't worry, if anything is ever done, it would still be available on CPAN.	[reply] [d/l] [select]
Re^5: Alternative to bytes::length() by assemble (Friar) on Dec 23, 2009 at 15:47 UTC
Re^6: Alternative to bytes::length() by ikegami (Patriarch) on Dec 23, 2009 at 16:04 UTC
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