Interval arithmetic for Ada 1.5

Interval arithmetic for Ada is a math library that provides an implementation of intervals for Ada. It includes arithmetic and relational operations.
Examples:
Tri-state logic
The package Intervals serves as a root package and also provides tri-state logic necessary to define relational operations on intervals. The type Logical is defined as:
type Logical is (False, True, Uncertain);
The following operations are defined for Logical:
function "not" (Left : Logical) return Logical;
function "and" (Left, Right : Logical) return Logical;
function "and" (Left : Logical; Right : Boolean)
return Logical;
function "and" (Left : Boolean; Right : Logical)
return Logical;
function "or" (Left, Right : Logical) return Logical;
function "or" (Left : Logical; Right : Boolean)
return Logical;
function "or" (Left : Boolean; Right : Logical)
return Logical;
function "xor" (Left, Right : Logical) return Logical;
function "xor" (Left : Logical; Right : Boolean)
return Logical;
function "xor" (Left : Boolean; Right : Logical)
return Logical;
Enhancements:
- For GNAT users GPS project files were included;
- Based on Measurement units for Ada v 2.4.