5. Intrinsic Subprograms
GNAT allows a user application program to write the declaration:
| | pragma Import (Intrinsic, name);
|
providing that the name corresponds to one of the implemented intrinsic
subprograms in GNAT, and that the parameter profile of the referenced
subprogram meets the requirements. This chapter describes the set of
implemented intrinsic subprograms, and the requirements on parameter profiles.
Note that no body is supplied; as with other uses of pragma Import, the
body is supplied elsewhere (in this case by the compiler itself). Note
that any use of this feature is potentially non-portable, since the
Ada standard does not require Ada compilers to implement this feature.
5.1 Intrinsic Operators
All the predefined numeric operators in package Standard
in pragma Import (Intrinsic,..)
declarations. In the binary operator case, the operands must have the same
size. The operand or operands must also be appropriate for
the operator. For example, for addition, the operands must
both be floating-point or both be fixed-point, and the
right operand for "**" must have a root type of
Standard.Integer'Base.
You can use an intrinsic operator declaration as in the following example:
| | type Int1 is new Integer;
type Int2 is new Integer;
function "+" (X1 : Int1; X2 : Int2) return Int1;
function "+" (X1 : Int1; X2 : Int2) return Int2;
pragma Import (Intrinsic, "+");
|
This declaration would permit "mixed mode" arithmetic on items
of the differing types Int1 and Int2.
It is also possible to specify such operators for private types, if the
full views are appropriate arithmetic types.
5.2 Enclosing_Entity
This intrinsic subprogram is used in the implementation of the
library routine GNAT.Source_Info. The only useful use of the
intrinsic import in this case is the one in this unit, so an
application program should simply call the function
GNAT.Source_Info.Enclosing_Entity to obtain the name of
the current subprogram, package, task, entry, or protected subprogram.
5.3 Exception_Information
This intrinsic subprogram is used in the implementation of the
library routine GNAT.Current_Exception. The only useful
use of the intrinsic import in this case is the one in this unit,
so an application program should simply call the function
GNAT.Current_Exception.Exception_Information to obtain
the exception information associated with the current exception.
5.4 Exception_Message
This intrinsic subprogram is used in the implementation of the
library routine GNAT.Current_Exception. The only useful
use of the intrinsic import in this case is the one in this unit,
so an application program should simply call the function
GNAT.Current_Exception.Exception_Message to obtain
the message associated with the current exception.
5.5 Exception_Name
This intrinsic subprogram is used in the implementation of the
library routine GNAT.Current_Exception. The only useful
use of the intrinsic import in this case is the one in this unit,
so an application program should simply call the function
GNAT.Current_Exception.Exception_Name to obtain
the name of the current exception.
5.6 File
This intrinsic subprogram is used in the implementation of the
library routine GNAT.Source_Info. The only useful use of the
intrinsic import in this case is the one in this unit, so an
application program should simply call the function
GNAT.Source_Info.File to obtain the name of the current
file.
5.7 Line
This intrinsic subprogram is used in the implementation of the
library routine GNAT.Source_Info. The only useful use of the
intrinsic import in this case is the one in this unit, so an
application program should simply call the function
GNAT.Source_Info.Line to obtain the number of the current
source line.
5.8 Rotate_Left
In standard Ada 95, the Rotate_Left function is available only
for the predefined modular types in package Interfaces. However, in
GNAT it is possible to define a Rotate_Left function for a user
defined modular type or any signed integer type as in this example:
| | function Shift_Left
(Value : My_Modular_Type;
Amount : Natural)
return My_Modular_Type;
|
The requirements are that the profile be exactly as in the example
above. The only modifications allowed are in the formal parameter
names, and in the type of Value and the return type, which
must be the same, and must be either a signed integer type, or
a modular integer type with a binary modulus, and the size must
be 8. 16, 32 or 64 bits.
5.9 Rotate_Right
A Rotate_Right function can be defined for any user defined
binary modular integer type, or signed integer type, as described
above for Rotate_Left.
5.10 Shift_Left
A Shift_Left function can be defined for any user defined
binary modular integer type, or signed integer type, as described
above for Rotate_Left.
5.11 Shift_Right
A Shift_Right function can be defined for any user defined
binary modular integer type, or signed integer type, as described
above for Rotate_Left.
5.12 Shift_Right_Arithmetic
A Shift_Right_Arithmetic function can be defined for any user
defined binary modular integer type, or signed integer type, as described
above for Rotate_Left.
5.13 Source_Location
This intrinsic subprogram is used in the implementation of the
library routine GNAT.Source_Info. The only useful use of the
intrinsic import in this case is the one in this unit, so an
application program should simply call the function
GNAT.Source_Info.Source_Location to obtain the current
source file location.
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