Re: Re: Distinguishing a v-string from something else

Good point. My context is that of a version number. Adding trailing zeros will not affect the ordering of greater/less, but will affect exact matches using eq (I figured stripping trailing zeros to normalize before comparing for equality).

A function that takes an IP address as a buffer of 4 bytes, a v-string (which will UTF-8-encode the values above 127), or a string can tell the difference by looking for the presence of only digits and dots and of the total length.

—John

Comment on Re: Re: Distinguishing a v-string from something else

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Re^3: Distinguishing a v-string from something else by particle (Vicar) on Dec 05, 2002 at 14:44 UTC
a v-string (which will UTF-8-encode the values above 127) actually, they're UTF-8 encoded if they're above 255. `> perl -MDevel::Peek -e"$a=v256;$b=v128;Dump$a;Dump$b" SV = PV(0x182ebf4) at 0x182383c REFCNT = 1 FLAGS = (POK,pPOK,UTF8) PV = 0x182013c "\304\200"\0 CUR = 2 LEN = 3 SV = PV(0x182ec24) at 0x1823848 REFCNT = 1 FLAGS = (POK,pPOK) PV = 0x182012c "\200"\0 CUR = 1 LEN = 2` [download] you can differentiate between a number and a v-string by examining the result of the SvPOKp(SV) macro. a true return means a v-string, false indicates a number. if you can differentiate between a v-string and any other string by your above method, you should be able to determine whether or not you have a v-string, no? ~Particle accelerates*	[reply] [d/l] [select]
Re: Re^3: Distinguishing a v-string from something else by John M. Dlugosz (Monsignor) on Dec 10, 2002 at 05:58 UTC
Re: actually, they're UTF-8 encoded if they're above 255. I just got around to verifying this. Actually, it does not work the same as `chr`, in that the v-string encoding faithfully follows the utf8 pragma, while chr decides for itself whether to return a byte or char oriented string regardless of the pragma setting. I'm wondering, though, if a number without a v and only 1 dot (normally a floating-point numeric constant) is dual-valued magic when parsed as the indirect object of a `use` or `require`? Have to peek at what comes into `VERSION`. if you can differentiate between a v-string and any other string by your above method, you should be able to determine whether or not you have a v-string, no? I can easily enough decide if I have a v-string or a string of the form "1.2.3.4" as ASCII, provided it has at least one dot in the latter. That's my purpose: to allow either as the value of $VERSION. —John	[reply] [d/l] [select]
Re^5: Distinguishing a v-string from something else by particle (Vicar) on Dec 10, 2002 at 11:53 UTC
i really hope you can get this going. the code on your pad looks like a fantastic start. i would suggest that if you do find a way to distinguish a v-string from anything else, you submit a patch to Scalar::Util. an isvstring sub would be very handy. ~Particle accelerates	[reply] [d/l]