Protect C++ Variables from Getting OverFlow ? if value is less UpperBound of any DataType

Question

I want to protect my variable from storing overflow values .

I am Calculating Loss at every level in a tree and at some stages.

1. it gives values like 4.94567e+302 ;Is this value Correct .If i compare it(Like Minimum ,Maximum etc) with any other values .Will it give the right answer?
2. Some Times it gives negative answer but Formula can not give negative values so surely this kind of value is wrong

I want to do Following thing in my c++ code .

ForExample:

long double loss;  //8 Bytes Floating Number
loss=calculate_loss(); 

if(loss value is greater than Capacity)
do
store 8 bytes in loss abd neglect remaining;
end if

Answer 1

There is a limits.h in C++, but this

if(loss value is greater than Capacity)

cannot work by definition. The value in loss can not be greater than its own data type maximum.

Your example value of 5 times 10^302 indeed is suspiciously large. Coupled with your statement that you sometimes get unexpected negative values, I suggest you take a good long look at your calculations.

A reasonable guess: you are tinkering with pointers and mix up pointers to integers and floating point numbers. But noone can tell without seeing the code.

Answer 2

if your capacity should be limited to the maximum or minimum capacity of the double (or float) datatype you can use floating point exceptions (not to be mistaken with C++ exceptions). Their signalling needs to be enabled in the compiler options and the you can map those to C++ exceptions detecting an overflow of the datatype.

here's an msdn page that describes the FP exceptions pretty good. At the bottom of the page you will find examples how to map that to C++ exceptions. http://msdn.microsoft.com/en-us/library/aa289157%28v=vs.71%29.aspx