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Overview
Comment:s_expressions-conditionals-generic_evaluate: new generic function providing a boolean expression evaluation framework
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: ca4b731098a8cfe14d7fe4e1a9e4ef683e63a360
User & Date: nat 2015-03-30 17:05:05.567
Context
2015-03-31
19:10
s_expressions-conditionals-strings: new package providing evaluation of boolean expressions about strings check-in: 048393b674 user: nat tags: trunk
2015-03-30
17:05
s_expressions-conditionals-generic_evaluate: new generic function providing a boolean expression evaluation framework check-in: ca4b731098 user: nat tags: trunk
2015-03-29
13:36
README: update with new packages check-in: 7bb056f68d user: nat tags: trunk
Changes
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     Ada 2012 container
  - `References`: generic simple reference-counter implementation
      - `Pools`: task-safe pool of referencesjj
  - `S-expressions`: library for dealing with [S-expressions][1]
      - `Atom_Buffers`: dynamic buffer for S-expression atoms
      - `Atom_Ref_Constructors`: helper constructors for atom references
      - `Atom_Refs`: common reference-counted atoms
      - `Conditionals`: S-expression boolean expressions about some object
          - `Generic_Evaluate`: Generic boolean expression evaluation framework
      - `Dynamic_Interpreters`: S-expression interpreter with mutable
        commands and callbacks
      - `Encodings`: translators to and from official S-expression encodings
      - `File_Readers`: objects reading a file to an atom or a S-expression
      - `File_Writers`: file-backed S-expression printer
      - `Generic_Caches`: memory container for S-expressions
      - `Interpeter_Loop`: inner loop of S-expression interpreters,
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Added src/natools-s_expressions-conditionals-generic_evaluate.adb. 










































































































































































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------------------------------------------------------------------------------
-- Copyright (c) 2015, Natacha Porté                                        --
--                                                                          --
-- Permission to use, copy, modify, and distribute this software for any    --
-- purpose with or without fee is hereby granted, provided that the above   --
-- copyright notice and this permission notice appear in all copies.        --
--                                                                          --
-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES --
-- WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF         --
-- MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR  --
-- ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES   --
-- WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN    --
-- ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF  --
-- OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.           --
------------------------------------------------------------------------------

with Natools.S_Expressions.Interpreter_Loop;

function Natools.S_Expressions.Conditionals.Generic_Evaluate
  (Context : in Context_Type;
   Expression : in out Lockable.Descriptor'Class)
  return Boolean
is
   type State_Type is record
      Result : Boolean;
      Conjunction : Boolean;
   end record;


   procedure Evaluate_Element
     (State : in out State_Type;
      Context : in Context_Type;
      Name : in Atom);
      --  Evaluate a name as part of an "and" or "or" operation

   procedure Evaluate_Element
     (State : in out State_Type;
      Context : in Context_Type;
      Name : in Atom;
      Arguments : in out Lockable.Descriptor'Class);
      --  Evaluate a name as part of an "and" or "or" operation

   function Internal_Evaluate
     (Context : in Context_Type;
      Name : in Atom)
     return Boolean;
      --  Evaluate a boolean name or a context name

   function Internal_Evaluate
     (Context : in Context_Type;
      Name : in Atom;
      Arguments : in out Lockable.Descriptor'Class)
     return Boolean;
      --  Evaluate a boolean function or a context function


   procedure Run is new Natools.S_Expressions.Interpreter_Loop
     (State_Type, Context_Type, Evaluate_Element, Evaluate_Element);


   ------------------------------
   -- Local Helper Subprograms --
   ------------------------------

   procedure Evaluate_Element
     (State : in out State_Type;
      Context : in Context_Type;
      Name : in Atom) is
   begin
      if State.Result = State.Conjunction then
         State.Result := Internal_Evaluate (Context, Name);
      end if;
   end Evaluate_Element;


   procedure Evaluate_Element
     (State : in out State_Type;
      Context : in Context_Type;
      Name : in Atom;
      Arguments : in out Lockable.Descriptor'Class) is
   begin
      if State.Result = State.Conjunction then
         State.Result := Internal_Evaluate (Context, Name, Arguments);
      end if;
   end Evaluate_Element;


   function Internal_Evaluate
     (Context : in Context_Type;
      Name : in Atom)
     return Boolean
   is
      S_Name : constant String := To_String (Name);
   begin
      if S_Name = "true" then
         return True;
      elsif S_Name = "false" then
         return False;
      else
         return Simple_Evaluate (Context, Name);
      end if;
   end Internal_Evaluate;


   function Internal_Evaluate
     (Context : in Context_Type;
      Name : in Atom;
      Arguments : in out Lockable.Descriptor'Class)
     return Boolean
   is
      State : State_Type;
      S_Name : constant String := To_String (Name);
   begin
      if S_Name = "and" then
         State := (True, True);
         Run (Arguments, State, Context);
         return State.Result;

      elsif S_Name = "or" then
         State := (False, False);
         Run (Arguments, State, Context);
         return State.Result;

      elsif S_Name = "not" then
         return not Generic_Evaluate (Context, Arguments);

      else
         return Parametric_Evaluate (Context, Name, Arguments);
      end if;
   end Internal_Evaluate;


   -------------------
   -- Function Body --
   -------------------

   Event : Events.Event;
   Lock : Lockable.Lock_State;
   Result : Boolean;
begin
   case Expression.Current_Event is
      when Events.Add_Atom =>
         Result := Internal_Evaluate (Context, Expression.Current_Atom);

      when Events.Open_List =>
         Expression.Lock (Lock);
         begin
            Expression.Next (Event);
            if Event = Events.Add_Atom then
               declare
                  Name : constant Atom := Expression.Current_Atom;
               begin
                  Expression.Next (Event);
                  Result := Internal_Evaluate (Context, Name, Expression);
               end;
            end if;
         exception
            when others =>
               Expression.Unlock (Lock, False);
               raise;
         end;
         Expression.Unlock (Lock);

      when Events.Close_List | Events.Error | Events.End_Of_Input =>
         raise Constraint_Error with "Conditional on empty expression";
   end case;

   return Result;
end Natools.S_Expressions.Conditionals.Generic_Evaluate;






Added src/natools-s_expressions-conditionals-generic_evaluate.ads.





















































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------------------------------------------------------------------------------
-- Copyright (c) 2015, Natacha Porté                                        --
--                                                                          --
-- Permission to use, copy, modify, and distribute this software for any    --
-- purpose with or without fee is hereby granted, provided that the above   --
-- copyright notice and this permission notice appear in all copies.        --
--                                                                          --
-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES --
-- WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF         --
-- MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR  --
-- ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES   --
-- WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN    --
-- ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF  --
-- OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.           --
------------------------------------------------------------------------------

------------------------------------------------------------------------------
-- Natools.S_Expressions.Conditionals.Generic_Evaluate provides an          --
-- evaluation function based on elementary names and functions, allowing    --
-- boolean combination of them.                                             --
-- For example Simple_Evaluate might evaluate the word "is_empty", while    --
-- Parameteric_Evaluate might check "contains", then Generic_Evaluate       --
-- handles expressions like:                                                --
-- (or is-empty (contains part_1) (and (not is-empty) (contains part_2)))   --
------------------------------------------------------------------------------

with Natools.S_Expressions.Lockable;

generic
   type Context_Type (<>) is limited private;

   with function Parametric_Evaluate
     (Context : in Context_Type;
      Name : in Natools.S_Expressions.Atom;
      Arguments : in out Natools.S_Expressions.Lockable.Descriptor'Class)
     return Boolean;

   with function Simple_Evaluate
     (Context : in Context_Type;
      Name : in Natools.S_Expressions.Atom)
     return Boolean;

function Natools.S_Expressions.Conditionals.Generic_Evaluate
  (Context : in Context_Type;
   Expression : in out Lockable.Descriptor'Class)
  return Boolean;
pragma Pure (Natools.S_Expressions.Conditionals.Generic_Evaluate);






Added src/natools-s_expressions-conditionals.ads.































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------------------------------------------------------------------------------
-- Copyright (c) 2015, Natacha Porté                                        --
--                                                                          --
-- Permission to use, copy, modify, and distribute this software for any    --
-- purpose with or without fee is hereby granted, provided that the above   --
-- copyright notice and this permission notice appear in all copies.        --
--                                                                          --
-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES --
-- WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF         --
-- MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR  --
-- ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES   --
-- WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN    --
-- ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF  --
-- OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.           --
------------------------------------------------------------------------------

------------------------------------------------------------------------------
-- Natools.S_Expressions.Conditionals is a common parent for all            --
-- conditional packages.                                                    --
------------------------------------------------------------------------------

package Natools.S_Expressions.Conditionals is
   pragma Pure;

end Natools.S_Expressions.Conditionals;