See Mini-Tutorial: Formats for Packing and Unpacking Numbers

F is for the build's NV
d is for the build's double

The sub requires an IEEE double.

There's no way to know if F is an IEEE double or not.
There's no way to know if d is an IEEE double or not.

But as far as I know, double and thus d is an IEEE double on all machines on which Perl currently runs.

But some people build Perl which uses long double for NV. So d is more reliable for a sub requiring an IEEE double.

But since you're more interested in inspecting an NV, F would make more sense for you. But you would also need to handle formats other than an IEEE double.

In reply to Re^5: Introspection into floats/NV by ikegami
in thread Introspection into floats/NV by LanX

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