[Ada] Dimensionnality Checking

[Arnaud Charlet <charlet at adacore dot com>]

The system is implemented in the GNAT compiler, and performs compile-time
checks to verify the dimensional consistency of physical computations.	
The system allows the user to define his own system of units, and imposes no
run-time changes nor multiple compilation passes on the user.
Indeed, the user is now able to create his own dimension system, to assign a
dimension with any subtypes and to run operations with dimensionned objects.
In that case, a dimensionnality checking will be performed.
If no dimension has been assigned, the compiler assumes that the item is
dimensionless.

The following gives an overall example of the dimensionality checking
system:

--
with System.Dim_Float_IO;

procedure Dimension_Test is

   --  CGS dimensioned type

   type CGS_Type is new Long_Float
     with Dimension_System =>
      ((Centimeter, "cm"),
       (Gram,       'g'),
       (Second,     's'));

   --  IO package for CGS_Type

   package CGS_IO is new System.Dim_Float_IO (CGS_Type);
   use CGS_IO;

   --  CGS dimensioned subtypes

   subtype Length is CGS_Type
     with Dimension => ("cm", Centimeter => 1, others => 0);

   subtype Mass is CGS_Type
     with Dimension => ("g", Gram => 1, others => 0);

   subtype Time is CGS_Type
     with Dimension => ('s', Second => 1, others => 0);

   --  CGS units

   cm : constant Length := 1.0;
   g  : constant Mass := 1.0;
   s  : constant Time := 1.0;

   --  Force dimensioned subtype

   subtype Force is CGS_Type
     with Dimension => ("dyn", 1, 1, -2);

   Random_Force : Force;

begin
   Random_Force := 2.1E+02 * cm * g * s**(-2);
   Put (Random_Force);
end Dimension_Test;

Tested on x86_64-pc-linux-gnu, committed on trunk

2011-12-15  Vincent Pucci  <pucci@adacore.com>

	* aspects.adb, aspects.ads Aspect_Dimension and
	Aspect_Dimension_System added
	* exp_ch6.adb (Expand_Call): Expand_Put_Call_With_Dimension_String
	case added
	* gcc-interface/Make-lang.in: s-llflex, sem_dim added.
	* impunit.adb :s-diflio and s-diinio defined as GNAT Defined
	Additions to System.
	* Makefile.rtl: s-diflio, s-diinio and s-llflex added
	* par-prag.adb, sem_prag.adb: Pragma_Dimension removed
	* rtsfind.ads: Expon_LLF added
	* sem_aggr.adb (Resolve_Aggregate): handles aggregate for
	Aspect_Dimension case
	* sem_attr.adb (Resolve_Attribute): analyze dimension for
	attribute
	* sem_ch10.adb (Analyze_With_Clause): Avoid the warning messages
	due to the use of a GNAT library for Dimension packages
	* sem_ch13.adb (Analyze_Aspect_Specifications):
	Aspect_Dimension and Aspect_Dimension_System cases added
	(Check_Aspect_At_Freeze_Point): Aspect_Dimension and
	Aspect_Dimension_System cases added
	* sem_ch2.adb (Analyze_Identifier): analyze dimension for
	identifier
	* sem_ch3.adb (Analyze_Component_Declaration): analyze dimension
	for component declaration (Analyze_Object_Declaration): analyze
	dimension for object declaration (Analyze_Subtype_Declaration):
	analyze dimension for subtype declaration
	* sem_ch4.adb (Operator_Check): checks exponent is a rational
	for dimensioned operand for a N_Op_Expon
	* sem_ch5.adb (Analyze_Assignment): analyze dimension for
	assignment (Analyze_Statements): removal of dimensions in all
	statements
	* sem_ch6.adb (Analyze_Return_Statement): analyze dimension for
	return statement
	* sem_ch8.adb (Analyze_Object_Renaming): analyze dimension for
	object renaming
	* sem_dim.adb, sem_dim.ads (Analyze_Aspect_Dimension):
	analyze the expression for aspect dimension and store the
	values in a Htable.
	(Analyze_Aspect_Dimension_System): analyze
	the expression for aspect dimension system and store the new
	system in a Table.
	(Analyze_Dimension): propagates dimension
	(Expand_Put_Call_With_Dimension_String): add the dimension
	string as a suffix of the numeric value in the output
	(Has_Dimension): return True if the node has a dimension
	(Remove_Dimension_In_Declaration): removal of dimension in the
	expression of the declaration.
	(Remove_Dimension_In_Statement): removal of dimension in statement
	* sem_res.adb (Resolve): analyze dimension if the node
	has already been analyzed.
	(Resolve_Arithmetic_Op): analyze
	dimension for arithmetic op.
	(Resolve_Call): analyze dimension for function call.
	(Resolve_Comparison_Op): analyze dimension for comparison op.
	(Resolve_Equality_Op): analyze dimension for equality op.
	(Resolve_Indexed_Component): analyze dimension for indexed component.
	(Resolve_Op_Expon): analyze dimension for op expon.
	(Resolve_Selected_Component): analyze dimension
	for selected component.
	(Resolve_Slice): analyze dimension for slice.
	(Resolve_Unary_Op): analyze dimension for unary op
	(Resolve_Type_Conversion): analyze dimension for type conversion
	(Resolve_Unchecked_Type_Conversion): analyze dimension for
	unchecked type conversion
	* snames.ads-tmpl Name_Dimension, Name_Dimension_System,
	Name_Dim_Float_IO, Name_Dim_Integer_IO,
	Name_Generic_Elementary_Functions, Name_Sqrt added.
	Pragma_Dimension removed
	* s-diflio.adb, s-diflio.ads New GNAT library generic package
	for dimensioned float type IO
	* s-diinio.adb, s-diinio.ads New GNAT library generic package
	for dimensioned integer type IO
	* s-llflex.ads (Expon_LLF): exponentiation routine for long long
	floats operand and exponent

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