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Real types provide approximations to the real numbers, with relative
bounds on errors for floating point types, and with absolute bounds for
fixed point types.
Syntax

real_type_definition ::=
floating_point_definition  fixed_point_definition
Static Semantics

A type defined by a real_type_definition is implicitly derived from
root_real, an anonymous predefined (specific) real type. Hence, all real
types, whether floating point or fixed point, are in the derivation
class rooted at root_real.

Real literals are all of the type universal_real, the universal type,
See section 3.4.1 Derivation Classes, for the class rooted at root_real, allowing their use with
the operations of any real type. Certain multiplying operators have a
result type of universal_fixed, See section 4.5.5 Multiplying Operators, the universal type for the
class of fixed point types, allowing the result of the multiplication or
division to be used where any specific fixed point type is expected.
Dynamic Semantics

The elaboration of a real_type_definition consists of the elaboration of
the floating_point_definition or the fixed_point_definition.
Implementation Requirements

An implementation shall perform the runtime evaluation of a use of a
predefined operator of root_real with an accuracy at least as great as
that of any floating point type definable by a
floating_point_definition.
Implementation Permissions

For the execution of a predefined operation of a real type, the
implementation need not raise Constraint_Error if the result is outside
the base range of the type, so long as the correct result is produced,
or the Machine_Overflows attribute of the type is false, See section G.2 Numeric Performance Requirements.

An implementation may provide nonstandard real types, descendants of
root_real that are declared outside of the specification of package
Standard, which need not have all the standard characteristics of a type
defined by a real_type_definition. For example, a nonstandard real type
might have an asymmetric or unsigned base range, or its predefined
operations might wrap around or "saturate" rather than overflow
(modular or saturating arithmetic), or it might not conform to the
accuracy model, See section G.2 Numeric Performance Requirements. Any type descended from a nonstandard real
type is also nonstandard. An implementation may place arbitrary
restrictions on the use of such types; it is implementation defined
whether operators that are predefined for "any real type" are defined
for a particular nonstandard real type. In any case, such types are not
permitted as explicit_generic_actual_parameters for formal scalar types
 See section 12.5.2 Formal Scalar Types.
NOTES

(32) As stated, real literals are of the anonymous predefined real type
universal_real. Other real types have no literals. However, the
overload resolution rules, See section 8.6 The Context of Overload Resolution, allow expressions of the type
universal_real whenever a real type is expected.
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