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6.3 Scalar Field Types

The rec format supports the declaration of fields of the following scalar types: integer numbers, ranges and real numbers.

Signed integers are supported by using the int declaration:

     %typedef: Id_t int

Given the declaration above, fields of type Id_t must contain integers, and they may be negative. Hexadecimal values can be written using the 0x prefix, and octal values using an extra 0. Valid examples are:

     %type: Id Id_t
     Id: 100
     Id: -23
     Id: -0xFF
     Id: 020

Sometimes it is desirable to reduce the range of integers allowed in a field. This can be achieved by using a range type declaration:

     %typedef: Interrupt_t range 0 15

Note that it is possible to omit the minimum index in ranges. In that case it is implicitly zero:

     %typedef: Interrupt_t range 15

It is possible to use the keywords MIN and MAX instead of a numeral literal in one or both of the points conforming the range. They mean the minimum and the maximum integer value supported by the implementation respectively. See the following examples:

     %typedef: Negative range MIN -1
     %typedef: Positive range 0 MAX
     %typedef: AnyInt range MIN MAX
     %typedef: Impossible range MAX MIN

Hexadecimal and octal numbers can be used to specify the limits in a range. This helps to define scalar types whose natural base is not ten, like for example:

     %typedef: Address_t range 0x0000 0xFFFF
     %typedef: Perms_t range 755

Real number fields can be declared with the real type specifier. A wide range of real numbers can be represented this way, only limited by the underlying floating point representation. The decimal separator is always the dot (.) character regardless of the locale setting. For example:

     %typedef: Longitude_t real

Examples of fields of type real:

     %rec: Rectangle
     %typedef: Longitude_t real
     %type: Width  Longitude_t
     %type: Height Longitude_t
     Width: 25.01
     Height: 10