Holds information about the various numeric (i.e.
scalar) types allowed by Eigen.
- Parameters:
-
| T | the numeric type at hand |
This class stores enums, typedefs and static methods giving information about a numeric type.
The provided data consists of:
- A typedef Real, giving the "real part" type of T. If T is already real, then Real is just a typedef to T. If T is
std::complex<U> then Real is a typedef to U.
- A typedef NonInteger, giving the type that should be used for operations producing non-integral values, such as quotients, square roots, etc. If T is a floating-point type, then this typedef just gives T again. Note however that many Eigen functions such as internal::sqrt simply refuse to take integers. Outside of a few cases, Eigen doesn't do automatic type promotion. Thus, this typedef is only intended as a helper for code that needs to explicitly promote types.
- A typedef Nested giving the type to use to nest a value inside of the expression tree. If you don't know what this means, just use T here.
- An enum value IsComplex. It is equal to 1 if T is a
std::complex type, and to 0 otherwise.
- An enum value IsInteger. It is equal to
1 if T is an integer type such as int, and to 0 otherwise.
- Enum values ReadCost, AddCost and MulCost representing a rough estimate of the number of CPU cycles needed to by move / add / mul instructions respectively, assuming the data is already stored in CPU registers. Stay vague here. No need to do architecture-specific stuff.
- An enum value IsSigned. It is equal to
1 if T is a signed type and to 0 if T is unsigned.
- An enum value RequireInitialization. It is equal to
1 if the constructor of the numeric type T must be called, and to 0 if it is safe not to call it. Default is 0 if T is an arithmetic type, and 1 otherwise.
- An epsilon() function which, unlike std::numeric_limits::epsilon(), returns a Real instead of a T.
- A dummy_precision() function returning a weak epsilon value. It is mainly used as a default value by the fuzzy comparison operators.
- highest() and lowest() functions returning the highest and lowest possible values respectively.
