unit uIntStack;

// This source is distributed under Apache 2.0

// Copyright (C) 2019-2021 Herbert M Sauro

// Author Contact Information:

// email: hsauro@gmail.com

// This is a lighweight integer stack. Implemented to ensure that

// the code can be used with Delphi versions that dodn't have

// generics

interface

Uses Classes, SysUtils;

const

MAX_STACK_ENTRIES = 100;

type

TStack = record

data : array of integer;

stackPtr : integer;

maxSize : integer;

end;

procedure create (var stack : TStack; n : integer);

procedure push (var stack : TStack; value : integer);

function pop (var stack : TStack) : integer;

function peek (var stack : TStack) : integer;

function getCount (var stack : TStack) : integer;

procedure clear (var stack : TStack);

function getSize (var stack : TStack) : integer;

implementation

procedure create (var stack : TStack; n : integer);

begin

stack.maxSize := n;

stack.stackPtr := -1;

setLength (stack.data, n);

end;

function getSize (var stack : TStack) : integer;

begin

result := stack.maxSize;

end;

procedure clear (var stack : TStack);

begin

stack.stackPtr := -1;

end;

function getCount (var stack : TStack) : integer;

begin

result := stack.stackPtr + 1;

end;

procedure push (var stack : TStack; value : integer);

begin

if stack.stackPtr = stack.maxSize then

raise Exception.Create('Integer stack overflow error.');

inc (stack.stackPtr);

stack.data[stack.stackPtr] := value;

end;

function pop (var stack : TStack) : integer;

begin

if stack.stackPtr = -1 then

raise Exception.Create('Integer stack underflow error.');

result := stack.data[stack.stackPtr];

dec (stack.stackPtr);

end;

function peek (var stack : TStack) : integer;

begin

result := stack.data[stack.stackPtr];

end;

end.