Returning Nan or Inf

This is a discussion on Returning Nan or Inf within the C Programming forums, part of the General Programming Boards category; I'm rewriting MatLab code into C and need to send values to a complex error function. The erfcomp function produces ...

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    Returning Nan or Inf

    I'm rewriting MatLab code into C and need to send values to a complex error function. The erfcomp function produces Nan and Inf values, but when I try to return these values to my other function and store them under a new variable, they somehow become numbers. My problem is that I need to stop a loop once Nan or Inf is reached.

    Is it possible to return Nan or Inf values to a function or I am I wasting my time by not looking for another approach to this?


    Thanks in advance.

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    Frequently Quite Prolix dwks's Avatar
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    I don't know how you can directly assign NaN to a variable in a program, but you can use isnan() to tell if a number is a Nan: http://www.opengroup.org/onlinepubs/...ons/isnan.html

    [edit] There's an isinf() as well. http://www.opengroup.org/onlinepubs/...ons/isinf.html [/edit]
    dwk

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    & the hat of GPL slaying Thantos's Avatar
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    Not sure how standard they are but my version of gcc has two macros, NAN and INFINITY.

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    Quote Originally Posted by dwks View Post
    you can use isnan() to tell if a number is a Nan: [/edit]

    I was planning on using isnan, but after I had already returned the value from the function. I was going to check the variable I saved it in using isnan or isinf. Otherwise, they don't do much for me because even if I check the values within the function, I can't break the loop from within the function. :/

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    Frequently Quite Prolix dwks's Avatar
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    INFINITY is C99, NAN is not. http://www.gnu.org/software/libtool/...y-and-NaN.html

    [edit] Hmm, strike that. NAN looks like it might be C99 too.
    C99 adds all sorts of stuff:
    ...
    -- macros INFINITY, NAN for special floating-point values
    http://std.dkuug.dk/jtc1/sc22/wg21/d...2002/n1372.txt

    Of course, the GCC page is likely more trustworthy than that source . . . . [/edit]
    Last edited by dwks; 07-01-2008 at 06:05 PM.
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
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