-1.#J outout of sprintf

I'm using sprintf to convert some struct with doubles into string

I'm using format "%.2f"

Code:

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double value;
printf("%.2f", value);

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Sometimes output is presented as following

Code:

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-1.#J

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I could not understand what can cause this type of output.
Could you link me to some reference?

It's a malformed floating point number. I'm not sure exactly what the #XX codes signify [and it's probably not much help anyways whether the number is "not a number" or "bad number" in some other way].

--
Mats

ok thanks

As a result of the above - another question

Code:

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struct a
{
  double b;
  double c;
  int d;
};

struct a array[2][2] = {{{0}}};

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I'd like to be sure that this code initializes all members of all 4 structs to zeros.

If not - how can I initialize all strcu members in the array above to zeroes in a portable way?
I'd like to avoid running loops on all struct members (there is a lot more than 3)

Yes, a struct and/or array will be filled to completion with zero if you do not supply a full set of initializer values.

--
Mats

Quote:

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Originally Posted by vart

ok thanks

As a result of the above - another question

Code:

---

struct a
{
  double b;
  double c;
  int d;
};

struct a array[2][2] = {{{0}}};

---

I'd like to be sure that this code initializes all members of all 4 structs to zeros.

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Yes, and you don't need the extra curly brackets.

Code:

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struct a array[2][2] = {0};

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Quote:

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Originally Posted by Banana Man

Yes, and you don't need the extra curly brackets.

Code:

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struct a array[2][2] = {0};

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That what I had - And got the above results with printf... so I'm not so sure now...

So have you verified that the value is actually zero?

--
Mats

Quote:

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That what I had - And got the above results with printf... so I'm not so sure now...

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What does this program print?

Code:

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#include <stdio.h>

struct a
{
  double b;
  double c;
  int d;
};

int main()
{
    struct a array[2][2] = {0};
    int i;
    int j;

    for ( i = 0; i < 2; ++i )
    {
        for ( j = 0; j < 2; ++j )
        {
            struct a *x = &array[i][j];

            printf("(%f,%f,%d)\t", x->b, x->c, x->d);
        }

        puts("");
    }

    return 0;
}

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Quote:

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Originally Posted by matsp

So have you verified that the value is actually zero?

--
Mats

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I'd like to...

How could I add assert on value that is printed as -1.#J?

I will add some asserts after initialization of the struct - to check if some values are not 0.
But I'd like to add some assert inside my calculations to catch the case when the double value gets corrupted...

Could I do it?

In C99, you've got some extra-fancy "is" tests, I think; there's "isnan", or even "fpclassify".

Quote:

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Originally Posted by vart

I'd like to...

How could I add assert on value that is printed as -1.#J?

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Quick and dirty:

Code:

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char buf[16];
snprintf(buf, 16, "%.2f", value);
if(strcmp(buf, "-1.#J") == 0)
{
    /* Caught it */
}

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That kind of sucks but it might be a good short-term method.

Looking at -1.#J, I almost want to say that it's trying to print an imaginary number, which would imply some kind of dramatic memory corruption affecting the "%.2f" string literal, but that seems far-fetched.

I'm using C89 on VS6.0 + Windows SDK

Quote:

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Originally Posted by vart

I'm using C89 on VS6.0 + Windows SDK

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In that case, replace my call to snprintf() with _snprintf() :)

Quote:

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Originally Posted by brewbuck

Quick and dirty:

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Thanks, It seems - I'll implement this solution...