Laying ground for general properties

src/alire-properties.ads

@@ -0,0 +1,33 @@
+private with Ada.Containers.Indefinite_Holders;
+
+package Alire.Properties with Preelaborate is
+
+   --  Properties are the general mechanism used to store all info about a release.
+   --  They can be specialized (e.g. in version, platform, compiler) but that can be transparent to the user.
+
+   type Property is tagged null record;
+
+
+
+   type Checker is tagged private;
+   --  A checker verifies against some internally stored data that a property is satisfied.
+   --  Here we provide the basic storage of values but the actual checking function must be overridden
+   --    for particular checks.
+
+   function New_Check (Using : Property'Class) return Checker'Class;
+
+   function Value (Check : Checker'Class) return Property'Class;
+
+   function Check (This : Checker'Class; Prop : Property'Class) return Boolean;
+   --  This classwide helper will match the stored property tag against the one given.
+   --  If the match the actual checking function is used, otherwise False is returned
+
+private
+
+   package Property_Holders is new Ada.Containers.Indefinite_Holders (Property'Class);
+
+   type Checker is tagged record
+      Property : Property_Holders.Holder;
+   end record;
+
+end Alire.Properties;