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FlexList II for C++
Copyright 1990
John W. Small
All rights reserved
PSW / Power SoftWare
P.O. Box 10072
McLean, Virginia 22102 8072
(703) 759-3838
11/28/90
CLAIM TO PROPRIETARY TECHNIQUES
Several features of FlexList used in combination make FlexList
unique and versatile. The hybrid stack-queue-list-array data
structure and the techniques used to implement it as a generic
polymorphic object can be easily ported to other computer
languages and remain intact in their essence. The author claims
all rights to these features.
SHAREWARE NOTICE
This FlexList packet is offered to you as "shareware" meaning try
before you buy. The shareware version allows you to test the
product to see if it's suitable for your purposes. In order to
legally use FlexList for any other purpose than to evaluate it,
you must first license it from PSW / Power SoftWare by sending in
a registration fee of $79.95. Upon registration you will receive
a printed version of the complete manual and source code.
SHAREWARE MANUAL
The shareware documentation that follows has been taken from the
actual printed FlexList manual. I've include only the most vital
information. Refer to flexlist.hpp for FlexList member function
prototypes.
Introduction
FlexList II is a lot more than just a ready-to-run C++ linked
list. It's a searchable-sortable-implodable generic
heterogeneous-homogeneous hybrid stack-queue-list-array
accessible by value, reference or node.
Anytime your C++ application requires a stack, queue, or linked
list, simply include flexlist.hpp in your source code and then
start defining your stack, queue, and/or list variables as type
FlexList. A FlexList can be initialized, by constructor, to
store any type of data and then accessed as a stack, queue, list,
or even an array interchangeably!
With more than 30 FlexList member functions to choose from, you
can push, pop, insert, delete, sort, store, recall, or find, to
name but a few. Access your data by value (copy) or by reference
(pointer). Or move nodes directly between FlexLists. Because
FlexList member functions adjust automatically to different types
of data, new sets of primitives needn't be derived to accommodate
new data types. Thus your application's coding time and code
size won't continue to grow when you add new types of FlexLists.
A FlexList can even be made to accommodate heterogeneous data via
its virtual member function hooks.
With FlexList you can quickly construct lists of lists or other
composite structures. And since FlexLists are initialized at run
time, the data they hold or even their creation can be specified
at run time thus allowing your application new dimensions of
adaptability to user inputs.
Use FlexList to code your next application's linked lists in
minutes instead of days, without the usual debugging and
documenting headaches associated with custom coding various list
types. It's no problem modifying your application in midstream
to incorporate various and differing list types; with FlexList no
linked list code needs to be scrapped or rewritten. The code
space you'll save over cloning list primitives for different data
types may just save you from having to go the overlay/swapping
route.
Chapter 2. Programming with FlexList
This chapter is a combination of a brief tutorial on using the
FlexList tool and a logical survey of the FlexList functions.
You may find it useful to lookup the FlexList functions in the
reference chapter while reading the example programs here. Don't
worry too much about the details for now. Instead you should
finish this chapter with
1) an idea of the points to remember when programming with
FlexList,
2) a conceptual model of FlexList's hybrid stack-queue-list-
array data structure, and
3) an appreciation for the various ways that a FlexList can be
manipulated and accessed, namely: by value, by reference, or
by node.
After programming for a while with FlexList, be sure to reread
this chapter.
Let's first cover several points that you should keep in mind
when using FlexList in any application.
1. Include flexlist.hpp in any application using FlexList.
#include <flexlist.hpp>
2. Define your stack, queue, or list as a FlexList, specifying
the size of the data it is to hold. To construct a FlexList
for stack of integers the code is:
FlexList intStack(sizeof(int));
3. The address of your data must be passed to FlexList member
functions. Remember, don't pass the data by value.
for (int i = 1; i < 11; i++)
intStack.pushD(&i); // address of i
4. FlexList member functions return pointers or integers. A
returned value of zero indicates failure of the function to
carry out its task.
while (intStack.popD(&i)) // loop until false
cout << i << "\n";
5. Don't forget to link your application with the object module
created by compiling flexlist.cpp or with the library you
build.
Let's see the whole program.
#include <iostream.h> // cout
#include <flexlist.hpp>
main() // Count backwards from ten via a stack.
{
FlexList intStack(sizeof(int));
for (int i = 1; i < 11; i++)
intStack.pushD(&i);
while (intStack.popD(&i))
cout << i << "\n";
}
Let's proceed with a survey of FlexList member functions.
FlexList Constructor/Destructor Functions
The FlexList class has two constructors and a virtual destructor.
FlexList(size_t sizeofNodeData, unsigned maxNodes
= FLmaxMaxNodes);
FlexList(unsigned sizeofCell, unsigned cells,
const void *array);
int clear(); // discards all FlexNodes in FlexList
virtual ~FlexList() { clear(); }
The first constructor you have already seen. It has a defaulted
second parameter that lets you set an upper limit on the number
of FlexNodes the FlexList is allowed to hold. FLmaxMaxNodes is
defined in flexlist.hpp as the maximum value an unsigned int can
obtain.
What's not obvious is if you construct a FlexList with the
sizeofNodeData parameter equal to zero you bring FlexList's
virtual functions into play that allow the FlexList to work with
variant data. The virtual functions in the FlexList base class
are set up to work with strings. Let's say you code the
following:
#define FLvariantData 0
#define FLstrings FLvariantData
FlexList strStack(FLstrings);
(FLvariantData and FLstrings are defined in flexlist.hpp.) The
FlexList will now work with strings. The FlexNodes will be just
big enough to hold strings within. If you derive a class from
FlexList and override the virtual functions then your derived
class can accommodate any type of object you want it to (see the
FlexList constructor entry in the reference chapter).
The second constructor allows you to explode a conventional C++
array (vector) into a FlexList.
The FlexList destructor is virtual so that your derived classes
can be destructed from code written to work on FlexLists. Such
is the case with composite FlexList structures.
FlexList Header Access Functions
As you become more familiar with what's inside a FlexList you
will want to access the data fields inside the FlexList header.
frontD() currentD() rearD()
CurNum() Nodes() MaxNodes()
setMaxNodes() notFull() SizeofNodeData()
isSorted() unSort() Compare()
setCompare() isFixed() isVariant()
A FlexList can be accessed as a stack, queue, list, or even an
array once it has nodes in it, interchangeably. The FlexList
header keeps track of everything so if your pushing data onto
your "stack" at one moment, you can recall an element from your
"array" the next. You can sort your FlexList, then perform
various other operations on it and isSorted will tell you if it
is still sorted. You can set an upper limit on the number of
nodes a FlexList is allowed to hold with setMaxNodes. You will
come to know what each function does with time.
FlexList Stack and Queue Functions
A stack provides LIFO (Last In, First Out) storage. A complete
set of stack primitives is provided. These functions don't
disturb the queue, list, or array structure of a FlexList. In
other words, you can access your FlexList as a stack at any time
and revert back to accessing it as a queue, list, or array
freely.
pushN() pushD() popN()
popD() topD() insQN()
insQD() frontD() rearD()
A queue provides FIFO (First In, First Out) storage. Notice that
some of the stack functions double up here as queue functions,
e.g. popD, topD. Also I have again included some of the FlexList
header access functions, i.e. frontD and rearD which return
pointers to the data in the first and last nodes respectively.
Basically I'm suggesting various logical ways to categorize
FlexList functions to help you remember them. You'll find that
several functions may belong in multiple categories.
The functions ending with "N" work directly with the FlexNodes
which contain your data. For an example, suppose that you want
to pop your stack directly into your queue. The following code
shows how.
#include <iostream.h> // cout
#include <flexlist.hpp>
int a[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
int *iptr;
#define inT0 ((int *)0)
main() /* count to ten the hard way */
{
FlexList s(sizeof(a[0]),sizeof(a)/sizeof(a[0]),a);
FlexList q(s.SizeofNodeData());
while ((iptr = (int *) q.insQN(s.popN())) != inT0)
cout << *iptr << "\n";
}
In this example the stack is constructed by "exploding" an array
of integers into a FlexList. Next the queue is constructed to
hold the same size data as the stack. Then the stack is popped
directly into the queue and a pointer to the data in the newly
inserted queue node is captured and tested to control the
looping! I print the integer each time so you can see that it
made it into the queue. Did you notice how I defined the NULL
integer pointer? I did that here so you'll know what's going on
when you see other NULL pointers elsewhere.
FlexList List Functions
Any FlexList can be treated as a doubly linked list thereby
providing sequential storage. You can insert nodes or delete
them. The FlexList header maintains a current node pointer that
lets the list functions know where the insertion or deletion is
to take place. Stack and queue functions don't disturb this
current pointer unless of course it points to the top/front of
the stack/queue and that node is popped/removed. In that case
the current node becomes undefined.
mkcur() insN() insD()
insSortN() insSortD() delN()
delD() nextD() prevD()
CurNum() currentD() Compare()
setCompare()
FlexList nodes are numbered starting at one. When nextD reaches
the end of the list the current node number is set to zero which
is said to be undefined and nextD returns the NULL void pointer.
On the next call to nextD the current node becomes one, that is
of course if there are nodes in the FlexList! PrevD works the
same way. This mechanism makes it handy to walk around lists
pausing at the ends. If you want to set the current pointer to a
particular node, use mkcur.
Oh, I guess I should mention again that you can store any type of
data in a FlexList not just integers. Let's see something like
that last example again with strings.
#include <iostream.h> // cout
#include <flexlist.hpp>
char *a[] = { "Now is the time", "for all good",
"programmers to cut", "their coding time",
"with FlexList!"
};
char **sptr;
#define chaRR char **
#define chaRR0 (chaRR)0
main() // PSW propaganda
{
FlexList l(sizeof(a[0]),sizeof(a)/sizeof(a[0]),a);
while ((sptr = (chaRR) l.nextD(0)) != (chaRR0))
cout << *sptr << "\n";
l.mkcur(l.Nodes());
while (l.delD(0))
/* null statement */; // l.clear();
cout << "\nThere should be zero nodes now: ";
cout << l.Nodes();
}
In this program I exploded a vector of char pointers into a
FlexList. Whenever FlexLists are constructed the current node is
set as undefined so nextD starts walking across the FlexList
beginning with the first node. NextD will copy the data in the
next node to whatever address you specify for the parameter
unless of course it is the NULL address! When you are browsing
the reference chapter you will notice many FlexList functions
that copy data to/from a FlexNode when an address is given. If
the NULL address is specified the copying action is inhibited but
the function otherwise performs its purpose.
In this example nextD is inhibited from copying any data but it
never the less moves the current pointer on to the next node.
NextD also returns a void pointer to the data in the next node.
I capture that pointer in order to print the string but I'm also
using it to control the loop.
All FlexList functions return either pointers or integer types
that are non zero only when the respective function completes
successfully. The void pointers returned from FlexList functions
point to the user data in focus. In the case of nextD it points
to the user data in the next node. I have simply type casted
this pointer to a pointer to the type of data I'm storing in the
FlexNodes in order to gain access to that data. As you can see
FlexList member functions allow you to access you data by value
(copy) or by reference (pointer) as well as moving nodes directly
between/within FlexLists.
Back to our example, mkcur moves the current node pointer to the
last node in the list. Mkcur also returns a pointer to the data
in the last node but I choose to ignore it. Now delD is used to
delete the nodes from the list. DelD removes the current node
after copying its contents to the address specified (copying is
inhibited here by the NULL address) and then unlinks the FlexNode
from the FlexList and proceeds to deallocate it making the
previous node in the FlexList the new current node. I might add
that insD does the exact opposite, i.e. inserts a new FlexNode
after the current node making the new node current. Again the
stack and queue structure of FlexList is undisturbed by any list
functions invoked on the FlexList and vice versa.
FlexList Search/Sort Functions
The Search/Sort functions allow you to lookup and/or sort your
data. Every FlexList has a user definable compare function. Use
setCompare to set a FlexList's internal compare function pointer.
To facilitate sorting define your compare function to return -1,
0, or 1 to indicate whether the first data being compared is less
than, equal to, or greater than the second, respectively. The
compare function is also used for matching in the find...()
functions. Please note that most of the functions mentioned here
modify the current node setting, thus they interact with the list
functions mentioned earlier.
insSortN() insSortD() findFirstD()
findNextD() findLastD() findPrevD()
sort() isSorted() unSort()
Compare() setCompare()
Use insSortD/N() to perform insertion sorts. If the list isn't
sorted then sort will be called automatically before attempting
the insertion. If a compare function pointer hasn't been setup
then the insertion is aborted.
The find...D functions work regardless if the FlexList is sorted
or not. If it is sorted then the binary search algorithm is used
to find the first/last matching data and a linear search is used
to find the next/previous match stopping immediately after the
first mismatch. If the FlexList is not sorted then the linear
search algorithm is used to find the first/last matching data and
again to find the next/previous match stopping only at the ends
of the list.
Use sort or setCompare to setup the compare function pointer. If
the NULL compare function pointer, FLcompare0 (defined in
flexlist.hpp), is passed to sort then the previous compare
function pointer is used to sort the list. Call isSorted to
determine whether a FlexList is still sorted from its last sort.
For example, suppose you sort a list and pop some nodes off the
front. Well that won't cause the FlexList to be unsorted so
isSorted will return true. But if you push some data onto it
treating it like a stack, that may or may not ruin the sorted
order. IsSorted will return false because it can no longer
guarantee that the FlexList is sorted. You need to be careful
though since nextD, prevD, and mkcur won't cause isSorted to
reset to false even though you might have modified the data in
the FlexNode via the returned void pointer! In that case you may
want to call unSort to reset isSorted so that it will return
false.
The following example performs an unsorted linear search followed
by an alphabetical sort.
#include <iostream.h> // cout
#include <string.h> // strstr, strcmp
#include <flexlist.hpp>
int strStr(char *s, char *t)
{
return !(int)strstr(s,t);
}
main()
{
FlexList l(FLstrings);
char *s, sbuf[80];
char *mask = "overtime";
l.insD("Once upon a time there were three");
l.insD("programmers, who worked");
l.insD("allot of overtime!");
l.insQD("That was before the FlexList Fox");
l.insQD("joined the staff!");
for (l.mkcur(0); l.nextD(sbuf);/* no reinit */)
cout << "\n Node: " << l.CurNum() << ". " << sbuf;
l.setCompare(FLcomparE(strStr));
if ((s = (char *)l.findFirstD(mask)) != (char *)0) {
cout << "\n Mask: \"" << mask << "\"";
cout << " found in node: " << l.CurNum();
cout << ". " << s;
}
l.sort(FLcomparE(strcmp));
for (unsigned i = 1; l.recallD(sbuf,i); i++) {
cout << "\n Node: " << l.CurNum();
cout << ". " << sbuf;
}
}
This program constructs a variant FlexList. The FlexNodes in
this FlexList are only be enough to hold the character strings
passed as parameters (please note that character string constants
are pointers to the strings so I didn't use the address of, "&",
operator!) I didn't use the second constructor because it builds
fixed size FlexNode (homogeneous) FlexLists - an array has fixed
cell sizes. Instead I inserted the strings one by one and queued
the last two just to be different.
The first "for loop" uses nextD to verify the contains of the
FlexNodes. NextD only copies the string and zero terminator
thanks to the virtual functions (see FlexList constructor entry
in the reference chapter to see how to construct heterogenous
lists). Be sure that the variable whose address you pass to
nextD is big enough to accommodate the largest data that can be
read! You should have noticed that I had to use mkcur(0) since
the current node pointer is still pointing to the last node
inserted and not the last node queued. Remember, queue functions
don't disturb the list structure - the current node concept is
part of the list structure, not the queue structure!
Since the list is not sorted, findFirstD searches in a linear
fashion starting with the first node, internally calling the
compare function setup with setCompare. The FLcomparE macro,
defined in flexlist.hpp, type casts strStr to the precise
function pointer type required by both setCompare and sort. My
strStr returns 0 if t is within s. Since only a linear search
will be used with this compare function, it doesn't matter that
is doesn't return -1 or 1 to indicate less than or greater than.
The program proceeds with a standard alphabetical sort and the
resultant ordering is displayed with recallD, an array access
function which you'll see in the next section.
FlexList Array Functions
An array provides randomly accessible storage. A FlexList can
also be accessed as an array once it has nodes in it.
storeD() recallD() mkcur()
currentD() CurNum()
The last node accessed becomes the new current node. When
randomly accessing a FlexList, mkcur is called internally by both
storeD and recallD to make the requested node current. Mkcur
determines which pointer (front, current, or rear) is closest to
the requested node. It then follows the FlexList's linkage from
that closest pointer to the newly requested node. The current
pointer is left positioned at the new node. Please note that
array, search/sort, and list functions interact in that they all
work with and modify the current node setting. Stack and queue
functions are independent, however.
FlexList Compaction Functions
Sometimes you want to work with a list, other times it's more
convenient to work with an array. Although FlexList allows this
chameleon behavior, your application may progress in stages that
favor a linked list at one point and a conventional array
(vector) at another. FlexList has "compaction" functions for
converting a FlexList into a conventional array or vice versa,
thus allowing you to optimize the performance of your
application.
FlexList() pack()
packPtrs()
You can think of the second FlexList constructor as exploding a
conventional array into a FlexList. Think of the pack member
function as doing the exact opposite or imploding a FlexList into
a conventional array. Arrays compacted by pack and packPtrs must
be explicitly deleted with a call to delete when no longer needed
if their memory is ever to be recovered for subsequent reuse.
PackPtrs returns an array of void pointers pointing to the data
in the FlexNodes. This array is NULL terminated to facilitate
subsequent processing.
For the last example program we'll clone a vector of char
pointers but the clone will have the advantage over its parent of
being sorted in alphabetical order.
#include <iostream.h> // cout
#include <string.h> // strcmp
#include <flexlist.hpp>
char *a[] = { "one", "two", "three", "four", "five" };
char **A;
int strCmp(char **s, char **t)
{
return strcmp(*s,*t);
}
main()
{
FlexList l(sizeof(a[0]),sizeof(a)/sizeof(a[0]),a);
l.sort(FLcomparE(strCmp));
A = (char **) l.pack();
for (int i = 0; i < sizeof(a)/sizeof(a[0]); i++)
cout << "\n a[" << i << "] = " << a[i];
if (A) {
for (i = 0; i < l.Nodes(); i++)
cout << "\n A[" << i << "] = " << A[i];
delete A;
}
}
Remember that the FlexNodes in this program contain char pointers
and that the compare function is passed pointers to the char
pointers, that is why the strCmp has to dereference them.
Many commercial toolbox functions require vector parameters.
With FlexList's compaction functions you can manipulate vectors
on the fly. The vectors can be stored in files and loaded as
needed via a FlexList and subsequent packing. The vector can
then be kept around only during the computation phase in which it
is needed. Large, oversized, static vectors need not be
allocated at compile time to cope with worst case scenarios,
consequently consuming precious data segment space within your
program.
Accessing FlexList Nodes and Data
Now that we've finished categorizing FlexList functions along the
lines of its hybrid stack-queue-list-array structure, let's
rethink what we've seen in terms of how the FlexList was
accessed, namely: by value, by reference, and by node. This
gives us a second way to analyze FlexList functions.
"By value" implies that the data is copied to or from a FlexNode.
For example, with popD the top node of the stack is popped and
the data is copied to the address specified by the parameter
before the node is freed and returned to the heap. We are in
effect accessing the data in the top node by value since we are
retrieving, in actuality, a copy of it.
popD(&i); // i is same type in FlexNode
"By reference" implies that the data in the FlexNode is accessed
by pointer. You will need to type cast these void pointers to
pointers to the type of data you have stored in the FlexNodes.
Suppose we're walking backward across a FlexList of integers with
the code:
while ((iptr = (int *)l.prevD(0)) != (int *)0)
cout "\n" << *iptr;
All void pointers returned by FlexList functions point to user
data. Thus the data can be modified directly. "By reference"
functions are provided to speed up processing. Without pointer
access you would have to first copy the data out of the FlexNode,
modify it and then copy it back. With large data structures that
could prove to be quite inefficient. Please note the nextD and
prevD are purely "by reference" when called with their parameters
equal to the NULL address. Actually all FlexList functions
returning void pointers allow access "by reference" in
combination perhaps with "by value" access.
In queuing network simulations you will want to move nodes
between FlexLists rapidly. Without access "by node" you would
have to "popD" the source queue and "insQD" the destination
queue. This would entail copying the data from the front node
into a local variable of the same type, unlinking and
deallocating the FlexNode, then reallocating a new FlexNode and
linking it into the other queue and finally copying the data from
the local variable back into the node. The faster way is to
unlink the FlexNode from the source queue and relink it directly
into the destination queue, e.g.
dstQ.insN(srcQ.popN());
If dstQ is already full then the node popped from srcQ is lost in
the twilight zone. A better approach would be to prevent the
chance of FlexNodes being left dangling:
while (dstQ.notFull() && srcQ.Nodes())
dstQ.insN(srcQ.popN());
The "By node" functions unlink and relink FlexNodes directly
between compatible FlexLists. Compatible in this sense means
that both FlexLists have equal sizeofNodeData fields (not
necessarily initialized for the same data type) . Use the
SizeofNodeData function to read the sizeofNodeData field. Two
FlexLists could also be considered to be compatible if they are
both variant FlexLists with compatible data. I should point out
that variant FlexLists have the sizeofNodeData fields set to
zero. Be careful not to assume that two FlexLists are compatible
just because both sizeofNodeData fields are equal to zero. You
are responsible for insuring that your FlexLists are compatible.
Remember also, FlexNodes unlinked with a function ending with "N"
must be relinked with a function ending with "N" to a compatible
FlexList or otherwise explicitly disposed of.
Summary
Let's review what we learned starting with the points to remember
when programming with the FlexList tool.
1. Be sure to include the FlexList header in any module
that references FlexList functions.
2. Define your stacks, queues, lists, etc. as "FlexList".
Define your dynamic versions as pointers to FlexLists,
i.e. "FlexL".
3. If the function is somehow involved with the copying of
user data, the address of the data is always passed.
4. All FlexList member functions return either pointers or
integers. A returned value of zero indicates failure
of the function to complete its task.
5. Link your application with the compiled flexlist object
module or the flexlist library you build.
Next, let's review the various functions available in the
FlexList tool. FlexList functions can be categorized according
to the logical nature of a FlexList's inherent hybrid stack-
queue-list-array structure.
FlexList Constructor/Destructors
FlexList() FlexList() clear()
~FlexList()
FlexList Header Access Functions
frontD() currentD() rearD()
CurNum() Nodes() MaxNodes()
setMaxNodes() notFull() SizeofNodeData()
isSorted() unSort() Compare()
setCompare() isFixed() isVariant()
FlexList Stack and Queue Functions
pushN() pushD() popN()
popD() topD() insQN()
insQD() frontD() rearD()
FlexList List Functions
mkcur() insN() insD()
insSortN() insSortD() delN()
delD() nextD() prevD()
CurNum() currentD() Compare()
setCompare()
FlexList Search/Sort Functions
insSortN() insSortD() findFirstD()
findNextD() findLastD() findPrevD()
sort() isSorted() unSort()
Compare() setCompare()
FlexList Array Functions
storeD() recallD() mkcur()
currentD() curNum()
FlexList Compaction Functions
FlexList() pack() packPtrs()
Finally, FlexLists can be accessed "by value", "by reference",
and "by node." "By value" entails the copying of user data
between the FlexNodes and user specified addresses. If the
address specified is NULL then the copying of data is inhibited
but the function performs otherwise as expected. The address is
always the first parameter of the FlexList function requiring it.
"By reference" infers that user data is manipulated directly
inside a FlexNode via a pointer. All FlexList functions
returning void pointers allow "by reference" access. "By node"
functions allow FlexNodes to be yanked/inserted from/into
FlexLists. These functions are named with "N" suffixes. Move
FlexNodes only between compatible FlexLists. Don't leave
FlexNodes dangling: either insert them back into a compatible
FlexList with an "N" function or explicitly delete them.
By now you should be ready to start the planning and subsequent
coding of your FlexList application with the help of the
reference chapter on FlexList functions. Later, when you feel
comfortable with FlexList, you will want to try your hand at
deriving your own variant FlexLists (lists that contain
heterogeneous data). Be sure to read the entry for the first
FlexList constructor in the reference chapter for an explanation
of writing your own FlexList virtual functions that accommodate
your heterogeneous data.
