When you modify the numeric value (NV) of a scalar, the NOK flag is set and the other flags (IOK, POK) are cleared: that means if we need the NV, we can just grab it (since NOK is true), but if we need the string value (PV, for 'pointer') we need to do a conversion.

When the conversion is done, we also need to distinguish whether the conversion was lossy or not: for example if we use a numeric 1.2 in an integer context, we cache the integer value 1 and set pIOK ('private' integer OK) to avoid the need to recalculate the integer next time we need it, but if it were 1.0 we'd also set IOK.

The Devel::Peek module is very useful for seeing this sort of thing:

  perl -MDevel::Peek -we '$a=1.2;Dump($a);$b="$a";Dump($a)'

[download]

Hugo

In reply to Re: Re: Re^4: Confirming what we already knew (it's cached) by hv
in thread Confirming what we already knew by AssFace

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