Re^2: "" but true

> For $x to be True, its first (number) argument needs to be true in numeric context && its second (string) argument needs to be true in string context.

Do you have a reference for this, or is it a guess?

I'm surprised since

I read boolean context be a sub case of numeric context
Perl tends to avoid such overhead like checking two slots

Cheers Rolf
_{(addicted to the Perl Programming Language :)

Wikisyntax for the Monastery}

Comment on Re^2: "" but true

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Re^3: "" but true by syphilis (Archbishop) on May 14, 2021 at 03:20 UTC
Do you have a reference for this, or is it a guess? I thought I had a reference for this ... but no, I completely misread this statement in the docs, relating to isdual(): `If $var is a scalar that has both numeric and string values, the resul +t is true` [download] Not only does it not pertain to dualvar(), but it doesn't say what I thought it said, anyway !! Additional experimentation suggests that, in fact, the dualvar will be True if the second arg is True. Is that the correct summation ? Thanks for catching. Not sure if that mistake necessarily impacts upon the little overload demo I provided. In any case, of course, that overload_true() subroutine can be tweaked to make it do whatever you want. I'll edit that post of mine. Cheers, Rob	[reply] [d/l]
Re^4: "" but true by Anonymous Monk on May 14, 2021 at 07:07 UTC
Re: Truth and Falsehood	[reply]
Re^5: "" but true by syphilis (Archbishop) on May 14, 2021 at 09:57 UTC
I followed your link. I did say the "the dualvar will be True if the second arg is True", and the second arg is the stringy arg. But you're right, I could have been more explicit - especially since LanX had speculated in the direction of "numeric context". (I missed an opportunity to score a point there !! ;-) Cheers, Rob	[reply]
Re^5: "" but true by LanX (Saint) on May 14, 2021 at 08:41 UTC
Yeah this makes sense since the string `" "` is true while it's numeric value is 0, so the stringy part must be tested if available. `DB<50> $a=" " DB<51> $b = $a+0 # $a will cache its numeric val DB<52> p !!$a # still true 1 DB<53> use Devel::Peek DB<54> Dump $a SV = PVNV(0x3fbd6f8) at 0x4aeebe0 REFCNT = 1 FLAGS = (POK,pIOK,pNOK,pPOK) IV = 0 # <-- integer NV = 0 PV = 0x4c4fb58 " "\0 # <-- string CUR = 1 LEN = 10 DB<55> Dump $b SV = NV(0x4aeedf0) at 0x4aeee08 REFCNT = 1 FLAGS = (NOK,pNOK) NV = 0 DB<56>` [download] Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery}	[reply] [d/l] [select]