[xacml] Numeric type conversion

[Michiharu Kudoh <KUDO@jp.ibm.com>]

Simon,

Re numeric type conversion, please refer to XPath 2.0 draft.
http://www.w3.org/TR/2002/WD-xpath20-20020816

Excerpt
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B Type Promotion and Operator Mapping
B.1 Type Promotion
Under certain circumstances, an atomic value can be promoted from one type
to another. The promotion rules listed below are used in basic type
conversions (see 2.4.3 Type Conversions) and during processing of
arithmetic expressions (see 3.4 Arithmetic Expressions) and value
comparisons (see 3.5.1 Value Comparisons). The rules may be applied
transitively. For example, since xs:integer is promotable to xs:decimal and
xs:decimal is promotable to xs:float, it follows that xs:integer is
promotable to xs:float, without necessarily passing through the
intermediate xs:decimal type.

The following type promotions are permitted:

A value of type xs:decimal can be promoted to the type xs:float. The result
is the xs:float value that is closest to the original value.

A value of type xs:float can be promoted to the type xs:double. The result
is the xs:double value that is the same as the original value.

A value of a derived type can be promoted to its base type. The result is
the base-type value that is the same as the original value. As an example
of this rule, a value of the derived type xs:integer can be promoted to its
base type xs:decimal.

Michiharu Kudo

IBM Tokyo Research Laboratory, Internet Technology
Tel. +81 (46) 215-4642   Fax +81 (46) 273-7428