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Predicate float64_codes_when/2
 float64_codes_when(?Value, ?Codes) is det[private]
Convert between a 64-bit floating point value and its wirestream codes. This is a low-level predicate; normally, you should use template_message/2 and the appropriate template term.

This predicate delays until either Value or Codes is sufficiently instantiated.

There is also a non-delayed float64_codes/2

Value- a floating point number
Codes- a list of 8 integers (codes)
- instantiation error if both Value and Codes are uninstantiated.
- May give misleading exception under some circumstances (e.g., float64_codes(_, [_,_,_,_,_,_,_,_]).