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    CGAL 4.7 - Number Types 
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#include <CGAL/utils_classes.h>
Not all values of a type need to be valid.
The function object class Is_valid checks this.
For example, an expression like NT(0)/NT(0) can result in an invalid number. Routines may have as a precondition that all values are valid.
Operations | |
| bool | operator() (const T &x) | 
| returns if the argument is valid.  More... | |
| bool CGAL::Is_valid< T >::operator() | ( | const T & | x | ) | 
returns if the argument is valid.