CGAL 5.1 - Algebraic Foundations
AlgebraicStructureTraits_::UnitPart Concept Reference


This AdaptableUnaryFunction computes the unit part of a given ring element.

The mathematical definition of unit part is as follows: Two ring elements \( a\) and \( b\) are said to be associate if there exists an invertible ring element (i.e. a unit) \( u\) such that \( a = ub\). This defines an equivalence relation. We can distinguish exactly one element of every equivalence class as being unit normal. Then each element of a ring possesses a factorization into a unit (called its unit part) and a unit-normal ring element (called its unit normal associate).

For the integers, the non-negative numbers are by convention unit normal, hence the unit-part of a non-zero integer is its sign. For a Field, every non-zero element is a unit and is its own unit part, its unit normal associate being one. The unit part of zero is, by convention, one.

See also


typedef unspecified_type result_type
 Is AlgebraicStructureTraits::Type.
typedef unspecified_type argument_type
 Is AlgebraicStructureTraits::Type.


result_type operator() (argument_type x)
 returns the unit part of \( x\).