## digitalmars.D - Check floats for .nan

- Acarion (7/7) Oct 07 2007 I have this code:
- BCS (7/16) Oct 07 2007 IIRC this will also pass:
- Daniel Keep (4/19) Oct 07 2007 You can also use (x!=x) to test to see if x is NaN, and (x==x) to make
- Janice Caron (5/6) Oct 07 2007 Are we really sure about that?
- Nathan Reed (5/13) Oct 07 2007 I believe you'd get a type error in that case (real and creal can't be
- Sean Kelly (7/22) Oct 07 2007 I tend to use:

I have this code: float number=getFloat(); assert(number!=float.nan); //this passes assert(to!(char[])(number)!="nan"); //this fails writefln(string.toString(number)); //this outputs: "nan" writefln( to!(char[])(to!(long)(number)) ); //this generates an error What did I do wrong?

Oct 07 2007

Reply to acarion,I have this code: float number=getFloat(); assert(number!=float.nan); //this passesIIRC this will also pass: assert(float.nan != float.nan); this is because D used IEEE floating point semantics. Under IEEE a comparison with NaN will always be not equal If you want to test for nan use "testedValue !<>= 0"* or the isnan functionassert(to!(char[])(number)!="nan"); //this fails writefln(string.toString(number)); //this outputs: "nan" writefln( to!(char[])(to!(long)(number)) ); //this generates an error What did I do wrong?* this is the not grater than, less than, or equal to operator.

Oct 07 2007

BCS wrote:Reply to acarion,You can also use (x!=x) to test to see if x is NaN, and (x==x) to make sure it is not NaN. -- DanielI have this code: float number=getFloat(); assert(number!=float.nan); //this passesIIRC this will also pass: assert(float.nan != float.nan); this is because D used IEEE floating point semantics. Under IEEE a comparison with NaN will always be not equal If you want to test for nan use "testedValue !<>= 0"* or the isnan function

Oct 07 2007

On 10/7/07, BCS <ao pathlink.com> wrote:If you want to test for nan use "testedValue !<>= 0"Are we really sure about that? If testedValue is complex (with non-zero real part) then it will not be less than 0, it will not be greater than zero, and it will not be equal to zero. But it will also not be NaN.

Oct 07 2007

Janice Caron wrote:On 10/7/07, BCS <ao pathlink.com> wrote:I believe you'd get a type error in that case (real and creal can't be directly compared, etc.) Haven't tried it though. Thanks, Nathan ReedIf you want to test for nan use "testedValue !<>= 0"Are we really sure about that? If testedValue is complex (with non-zero real part) then it will not be less than 0, it will not be greater than zero, and it will not be equal to zero. But it will also not be NaN.

Oct 07 2007

BCS wrote:Reply to acarion,I tend to use: testedValue !<>= testedValue Though I've occasionally wondered whether the 'is' identity operator should work for checking against nan: testedValue is float.nan SeanI have this code: float number=getFloat(); assert(number!=float.nan); //this passesIIRC this will also pass: assert(float.nan != float.nan); this is because D used IEEE floating point semantics. Under IEEE a comparison with NaN will always be not equal If you want to test for nan use "testedValue !<>= 0"* or the isnan function

Oct 07 2007