Catch Math Function exception

If we want to use a mathematical function, such as the inverse of the string function asin (x), if the value of the variable x is provided by the user or an intermediate result, then the call must be judged to be a reasonable range of values, whether full |x|<=1? That

if(fabs(x)<=1)
　 y=asin(x);
else
　 y=…

Logarithmic functions can also be handled similarly. However, if the Power function pow (x,y) is encountered, the problem is not so simple. Careful analysis will find:

Y X	Negative decimal	Negative integer	0	Integer	Decimal
Negative decimal	No meaning	Make sense	Make sense	Make sense	No meaning
Negative integer	No meaning	Make sense	Make sense	Make sense	No meaning
0	No meaning	No meaning	Make sense	Make sense	Make sense
Integer	Make sense	Make sense	Make sense	Make sense	Make sense
Decimal	Make sense	Make sense	Make sense	Make sense	Make sense

For example: Pow ( -1.2,-1.2) =-1. #IND. If you want to process it programmatically, you need at least six if statements. Even so, there is the trouble: how to determine the value of a double variable is an integer or a decimal?

In order to deal with the anomalies appearing in mathematical function operations, VC + + provides a function _mather, whose prototype is in <math.h>:

int _matherr( struct _exception *except );

In order to take advantage of this function, you simply define one such function where the mathematical function is applied, such as

#include <math.h>
#include <stdio.h>
void Main ()
{
	double x,y,z;
	x=-1.23;
	Y=-1;
	Z=pow (x,y);
	printf ("%g\n", z);
	y=-1.1;
	Z=pow (x,y);
	printf ("%g\n", z);
}
int _matherr (struct _exception *except)
{char* errorstring[] = {"_domain", "_sing"
, "_overflow", "_ploss", c16/> "_tloss", "_underflow"};
	printf ("Error function name is%s\n", except->name);
	printf ("The Varianbles arg1=%g,arg2=%g\n", except->arg1,except->arg2);
	printf ("The Error type =%s\n", Errorstring[except->type]);
	printf ("The Error value=%g\n", except->retval);
	except->retval=1234;
	printf ("After handling error value=%g\n", except->retval);
	return 1;
}