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How to use _matherror...?

Posted on 1998-03-10
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Last Modified: 2010-05-18
How can I use the _matherror function in my VC++ program?

I have looked in the on-line help and done some copy-paste but I can't make it working. According to a friend I probably have to do set some flag somewhere...

I would like to use the _matherror function to check handle asin() error.

When replying to this question ,if possible, please send me a clear answer.

Thank you very much in advance.

/mfonko
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Question by:mtonko
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4 Comments
 
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Expert Comment

by:q2guo
ID: 1183331
Can you post your code here please?
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Expert Comment

by:nietod
ID: 1183332
What problems are you having?
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Accepted Solution

by:
AlFa earned 40 total points
ID: 1183333
/* MATHERR.C illustrates writing an error routine for math
 * functions. The error function must be:
 *      _matherr
 */

#include <math.h>
#include <string.h>
#include <stdio.h>

void main()
{
    /* Do several math operations that cause errors. The _matherr
     * routine handles _DOMAIN errors, but lets the system handle
     * other errors normally.
     */
    printf( "log( -2.0 ) = %e\n", log( -2.0 ) );
    printf( "log10( -5.0 ) = %e\n", log10( -5.0 ) );
    printf( "log( 0.0 ) = %e\n", log( 0.0 ) );
}

/* Handle several math errors caused by passing a negative argument
 * to log or log10 (_DOMAIN errors). When this happens, _matherr
 * returns the natural or base-10 logarithm of the absolute value
 * of the argument and suppresses the usual error message.
 */
int _matherr( struct _exception *except )
{
    /* Handle _DOMAIN errors for log or log10. */
    if( except->type == _DOMAIN )
    {
        if( strcmp( except->name, "log" ) == 0 )
        {
            except->retval = log( -(except->arg1) );
            printf( "Special: using absolute value: %s: _DOMAIN "
                     "error\n", except->name );
            return 1;
        }
        else if( strcmp( except->name, "log10" ) == 0 )
        {
            except->retval = log10( -(except->arg1) );
            printf( "Special: using absolute value: %s: _DOMAIN "
                     "error\n", except->name );
            return 1;
        }
    }
    else
    {
        printf( "Normal: " );
        return 0;    /* Else use the default actions */
    }
}

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Expert Comment

by:q2guo
ID: 1183334
AlFa nice job on the cut and paste.  I think mtonko already tried this.
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