MATHERR(3M) BSD MATHERR(3M)
NAME
matherr - error-handling function
SYNOPSIS
#include <math.h>
int matherr (x)
struct exception *x;
DESCRIPTION
matherr is invoked by functions in the Math Library when errors are
detected. Users may define their own procedures for handling errors, by
including a function named matherr in their programs. matherr must be of
the form described above. When an error occurs, a pointer to the
exception structure x will be passed to the user-supplied matherr
function. This structure, which is defined in the <math.h> header file,
is as follows:
struct exception {
int type;
char *name;
double arg1;
double arg2;
double retval;
};
The element type is an integer describing the type of error that has
occurred. It is taken from following list of constants (defined in the
header file):
DOMAIN argument domain error
SING argument singularity
OVERFLOW overflow range error
UNDERFLOW underflow range error
TLOSS total loss of significance
PLOSS partial loss of significance
The element name points to a string containing the name of the function
that incurred the error. The variables arg1 and arg2 are the arguments
with which the function was invoked. retval is set to the default value
that will be returned by the function unless the user's matherr sets it
to a different value.
If the user's matherr function returns nonzero, no error message will be
printed, and errno will not be set.
If matherr is not supplied by the user, the default error-handling
procedures, described with the math functions involved, will be invoked
upon error. These procedures are also summarized in the table below. In
every case, errno is set to EDOM or ERANGE and the program continues.
EXAMPLE
#include <math.h>
int
matherr(x)
register struct exception *x;
{
switch (x->type) {
case DOMAIN:
/* change sqrt to return sqrt(-arg1), not 0 */
if (!strcmp(x->name, "sqrt")) {
x->retval = sqrt(-x->arg1);
return (0); /* print message and set errno */
}
case SING:
/* all other domain or sing errors, print message and abort */
fprintf(stderr, "domain error in %s\n", x->name);
abort( );
case PLOSS:
/* print detailed error message */
fprintf(stderr, "loss of significance in %s(%g) = %g\n",
x->name, x->arg1, x->retval);
return (1); /* take no other action */
}
return (0); /* all other errors, execute default procedure */
}
______________________________________________________________________________
|_____________________DEFAULT_ERROR_HANDLING_PROCEDURES_______________________|
|_______________________|_____________________________________________________|
|_______________________|__________________Types_of_Errors____________________|
|_______________________|_______|_______|__________|__________|_______|_______|
|_________type__________|DOMAIN_|_SING__|OVERFLOW__|UNDERFLOW_|TLOSS__|PLOSS__|
|_______________________|_______|_______|__________|__________|_______|_______|
|_________errno_________|_EDOM__|_EDOM__|_ERANGE___|__ERANGE__|ERANGE_|ERANGE_|
|_______________________|_______|_______|__________|__________|_______|_______|
|BESSEL:________________|__-____|__-____|____-_____|____-_____|_M,_0__|__*____|
|y0, y1, yn (arg < 0) |M, -H | - | - | - | - | - |
|_______________________|_______|_______|__________|__________|_______|_______|
|EXP: | - | - | H | 0 | - | - |
|_______________________|_______|_______|__________|__________|_______|_______|
|LOG, LOG10: | | | | | | |
|_______________________|_______|_______|__________|__________|_______|_______|
|_(arg_<_0)_____________|M,_-H__|__-____|____-_____|____-_____|__-____|__-____|
| (arg = 0) | - |M, -H | - | - | - | - |
|_______________________|_______|_______|__________|__________|_______|_______|
|POW: | - | - | +H | 0 | - | - |
|_______________________|_______|_______|__________|__________|_______|_______|
|neg_**_non-int_________|M,_0___|__-____|____-_____|____-_____|__-____|__-____|
| 0 ** non-pos | | | | | | |
|_______________________|_______|_______|__________|__________|_______|_______|
|SQRT: | M, 0 | - | - | - | - | - |
|_______________________|_______|_______|__________|__________|_______|_______|
|GAMMA: | - | M, H | H | - | - | - |
|_______________________|_______|_______|__________|__________|_______|_______|
|HYPOT: | - | - | H | - | - | - |
|_______________________|_______|_______|__________|__________|_______|_______|
|SINH: | - | - | +H | - | - | - |
|_______________________|_______|_______|__________|__________|_______|_______|
|COSH: | - | - | H | - | - | - |
|_______________________|_______|_______|__________|__________|_______|_______|
|SIN, COS, TAN: - | - | - | - | M, 0 | * | |
|_______________________|_______|_______|__________|__________|_______|_______|
|ASIN, ACOS, ATAN2: M, 0| - | - | - | - | - | |
|_______________________|_______|_______|__________|__________|_______|_______|
_____________________________________________________
| ABBREVIATIONS |
| * As much as possible of the value is returned. |
| M Message is printed (EDOM error). |
| H HUGE is returned. |
| -H -HUGE is returned. |
| +H HUGE or -HUGE is returned. |
| 0 0 is returned. |
|____________________________________________________|