Query: matherr
OS: ultrix
Section: 3m
Format: Original Unix Latex Style Formatted with HTML and a Horizontal Scroll Bar
matherr(3m) matherr(3m) Name matherr - error-handling function for System V math library Syntax #include <math.h> int matherr (x) struct exception *x; Description The subroutine is invoked by functions in the System V Math Library when errors are detected. Users may define their own procedures for handling errors by including a function named in their programs. The subroutine must be of the form described above. A pointer to the exception structure x will be passed to the user-supplied function when an error occurs. This structure, which is defined in the <math.h> header file, is as follows: struct exception { int type; char *name; double arg1, arg2, retval; }; The element type is an integer describing the type of error that has occurred, from the following list of constants (defined in the header file): DOMAIN domain error SING singularity OVERFLOW overflow UNDERFLOW underflow TLOSS total loss of significance PLOSS partial loss of significance The element name points to a string containing the name of the function that had the error. The variables arg1 and arg2 are the arguments to the function that had the error. The retval is a double that is returned by the function having the error. If it supplies a return value, the user's must return nonzero. If the default error value is to be returned, the user's must return 0. If 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 nonzero and the program continues. Examples matherr(x) register struct exception *x; { switch (x->type) { case DOMAIN: case SING: /* print message and abort */ fprintf(stderr, "domain error in %s ", x->name); abort( ); case OVERFLOW: if (!strcmp("exp", x->name)) { /* if exp, print message, return the argument */ fprintf(stderr, "exp of %f ", x->arg1); x->retval = x->arg1; } else if (!strcmp("sinh", x->name)) { /* if sinh, set errno, return 0 */ errno = ERANGE; x->retval = 0; } else /* otherwise, return HUGE */ x->retval = HUGE; break; case UNDERFLOW: return(0); /* execute default procedure */ case TLOSS: case PLOSS: /* print message and return 0 */ fprintf(stderr, "loss of significance in %s ", x->name); x->retval = 0; break; } return(1); } +-------------------------------------------------------------------------------------------------------------------------------------------------+ | | DEFAULT ERROR HANDLING PROCEDURES | | | | +----------------------+--------------------------+-----------------+--------------------+----------------------+-----------------+---------------+ | | Types of Errors | | | | | | +----------------------+--------------------------+-----------------+--------------------+----------------------+-----------------+---------------+ | | DOMAIN | SING | OVERFLOW | UNDERFLOW | TLOSS | PLOSS | +----------------------+--------------------------+-----------------+--------------------+----------------------+-----------------+---------------+ | BESSEL: | - | - | H | 0 | M, 0 | * | | y0, y1, yn | M, -H | - | - | - | - | - | | (neg. no.) | | | | | | | +----------------------+--------------------------+-----------------+--------------------+----------------------+-----------------+---------------+ | EXP: | - | - | H | 0 | - | | +----------------------+--------------------------+-----------------+--------------------+----------------------+-----------------+---------------+ | POW: | - | - | H | 0 | - | - | | (neg.)**(non- | M, 0 | - | - | - | - | - | | int.), 0**0 | | | | | | | +----------------------+--------------------------+-----------------+--------------------+----------------------+-----------------+---------------+ | LOG: | | | | | | | | log(0): | - | M, -H | - | - | - | - | | log(neg.): | M, -H | - | - | - | - | - | +----------------------+--------------------------+-----------------+--------------------+----------------------+-----------------+---------------+ | SQRT: | M, 0 | - | - | - | - | - | +----------------------+--------------------------+-----------------+--------------------+----------------------+-----------------+---------------+ | GAMMA: | - | M, H | - | - | - | - | +----------------------+--------------------------+-----------------+--------------------+----------------------+-----------------+---------------+ | HYPOT: | - | - | H | - | - | - | +----------------------+--------------------------+-----------------+--------------------+----------------------+-----------------+---------------+ | SINH, COSH: | - | - | H | - | - | - | +----------------------+--------------------------+-----------------+--------------------+----------------------+-----------------+---------------+ | SIN, COS: | - | - | - | - | M, 0 | * | +----------------------+--------------------------+-----------------+--------------------+----------------------+-----------------+---------------+ | TAN: | - | - | H | - | M, 0 | * | +----------------------+--------------------------+-----------------+--------------------+----------------------+-----------------+---------------+ | ACOS, ASIN: | M, 0 | - | - | - | - | - | +----------------------+--------------------------+-----------------+--------------------+----------------------+-----------------+---------------+ +----------------------------------------------------+ | ABBREVIATIONS | | * As much as possible of the value is returned. | | M Message is printed. | | H HUGE is returned. | | -H -HUGE is returned. | | 0 0 is returned. | +----------------------------------------------------+ VAX matherr(3m)