Question

i want to test some code to make sure it handles NAN, INF and -INF inputs properly.

i know there exists functions that return NAN, INF and -INF, but as a Double:

unit IEEE754;
...
function NAN: Double;
function PositiveInfinity:  Double;
function NegativeInfinity:  Double;

Except in my case i need to test when a Currency is one of these three edge-case values. Unfortunatly you cannot convert any of these to a Double:

Test(NAN);

procedure Test(const Value: Currency);
  ...

There’s an EInvalidOp Invalid floating point operation exception when converting a Double NAN to a Currency.

Is it possible to assign a NAN to a Currency?

Perhaps, rather than it being possible to assign a NAN to a Currency, it is instead not possible – and i can just ignore this edge case.

Can i ignore this edge case?

Is it possible to “Set a Currency value to NAN, INF or -INF?”

---

{   David Heffernan says it's impossible for a currency to contain INF,-INF or NAN.
    So there's no need to test for it.
    http://stackoverflow.com/questions/7096966/set-a-currency-value-to-nan-inf-or-inf

    //Handle NaN, where exponent is -32767
    test(NAN, 'NAN');

    //Handle +inf, where exponent is 32767 and Negative is true
    test(PositiveInfinity, 'INF');

    //Handle -inf, where expondent is 32767 and Negative is true
    test(NegativeInfinity, '-INF');
}

Answer 1

Currency is not an IEEE754 float type and does not have NAN or INF values.

The documentation explains that Currency is implemented as a 64 bit integer with implicit scale of 10000 and that the range of possible values is -922337203685477.5808 to 922337203685477.5807. Since this covers the full range of a 64 bit integer it follows that there are no bit patterns available for sentinel values like NAN or INF.