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-------------------------------------------------------------------------------
-- (C) Altran Praxis Limited
-------------------------------------------------------------------------------
--
-- The SPARK toolset is free software; you can redistribute it and/or modify it
-- under terms of the GNU General Public License as published by the Free
-- Software Foundation; either version 3, or (at your option) any later
-- version. The SPARK toolset is distributed in the hope that it will be
-- useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
-- Public License for more details. You should have received a copy of the GNU
-- General Public License distributed with the SPARK toolset; see file
-- COPYING3. If not, go to http://www.gnu.org/licenses for a complete copy of
-- the license.
--
--=============================================================================
--------------------------------------------------------------------------------
-- StmtStack
--
-- Purpose:
-- StmtStack is an Abstract State Machine that provides a simple
-- stack of entries. Each entry contains a pair of values:
--
-- StmtNumber - the number of a BPG statement node, with
-- ZERO indicating a null entry, and a positive
-- number interpreted as a value of type Graph.MatrixIndex
--
-- Kind - the class of statement, as defined by ArcKind below.
--
-- Clients:
-- The StmtStack is used by the (iterative) traversal algorithm in
-- DAG.BuildGraph to keep track of the nesting of statement forms in the
-- syntax tree as the BPG is produced.
--
-- Use:
-- See DAG.BuildGraph
--
-- Extension:
-- None planned at present.
--------------------------------------------------------------------------------
with ExaminerConstants;
--# inherit ExaminerConstants,
--# SystemErrors;
package StmtStack
--# own S : StmtStacks;
--# initializes S;
is
type ArcKind is (
Elementary,
IfStart,
IfTrueBranch,
IfFalseBranch,
CaseStart,
CaseBranch,
CaseExit,
LoopStart,
LoopExit);
type StmtRecord is record
StmtNmbr : Natural;
Kind : ArcKind;
end record;
subtype StmtRange is Integer range 0 .. ExaminerConstants.StmtStackSize;
type StmtVector is array (StmtRange) of StmtRecord;
type StmtStacks is record
Vector : StmtVector;
Pointer : StmtRange;
end record;
function IsEmpty return Boolean;
--# global in S;
function Top return StmtRecord;
--# global in S;
procedure Clear;
--# global out S;
--# derives S from ;
-- Pop, but fatal error if underflow
procedure Pop;
--# global in out S;
--# derives S from *;
-- Push, but fatal error if overflow
procedure Push (R : in StmtRecord);
--# global in out S;
--# derives S from *,
--# R;
-- Print the current state of the stack to Standard_Output via Debug package,
-- preceding by the given Msg
procedure Dump_Stack (Msg : in String);
--# global in S;
--# derives null from Msg,
--# S;
end StmtStack;
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