_matherb

_matherb

Handle Math Function Error (Binary Floating Point)

Portability: C99

SYNOPSIS
DESCRIPTION
RETURN VALUE
PORTABILITY
IMPLEMENTATION
RELATED FUNCTIONS
SEE ALSO

SYNOPSIS

   #include <lcmath.h>

   int _matherb(struct exception *x);

DESCRIPTION

_matherb is called whenever an IEEE transcendental function detects an error. _matherb receives an exception block as an argument describing the error. This structure is defined in <lcmath.h>:

   struct exception {
      int type;          /* error type */
      _ _near char *name; /* name of failed function */
      double arg1;       /* first argument */
      double arg2;       /* second argument */
      double retval;     /* proposed return value */
      int flterr;        /* if non-0, failing function returns float */
   };

The error type names defined in <lcmath.h> are:

Error Type Definition

DOMAIN domain error

SING singularity

OVERFLOW overflow

UNDERFLOW underflow

TLOSS total loss of significance

PLOSS partial loss of significance

Error Type	Definition
DOMAIN	domain error
SING	singularity
OVERFLOW	overflow
UNDERFLOW	underflow
TLOSS	total loss of significance
PLOSS	partial loss of significance

RETURN VALUE

If _matherb returns 0, a diagnostic message is written to the standard error file (stderr). If _matherb returns a nonzero value, the diagnostic message is suppressed, and the calling function will return the value stored in retval to its caller.

PORTABILITY

Traditional UNIX C compilers support the functionality of _matherb using the name matherr. Unfortunately, using the name matherr conflicts with the ANSI Standard. However, the header file lcmath.h contains the following macro:

   #define matherr _matherb

If you include this header file, use the name that is compatible with traditional UNIX C compilers.

IMPLEMENTATION

The standard version of _matherb supplied in the library places the appropriate error number into the external integer errno and returns zero. When _matherb is called, the function that detected the error places its proposed return value into the exception structure. The zero return code indicates that the proposed return value should not be changed.

Supply your own version of _matherb if desired. On particular errors, it may be desirable to cause the function detecting the error to return a value other than its usual default. You can accomplish this by storing a new return value in retval of the exception structure and then returning a nonzero value from _matherb, which forces the function to pick up the new value from the exception structure. If a nonzero value is returned, a diagnostic message is not printed for the error.

RELATED FUNCTIONS

_matherr, quiet

SEE ALSO

"Mathematical Functions" in Chapter 2, "Function Categories"

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