sad when only thing being posted is the rules frmo the moderator.

--- Renegade v11-26.3 DOS
* Origin: The Titantic BBS Telnet - ttb.slyip.com (1:129/305)

Quoting Tony Master to All <=-

sad when only thing being posted is the rules frmo the moderator.

Well I guess no one needs lessons :)



... "You're a vicious man." "It's in the job description!"
--- Fringe BBS
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|03Quoting message from |11Scott Adams |03to |11Tony Master
|03on |1103 Dec 03 16:09:14|03.

Quoting Tony Master to All <=-

sad when only thing being posted is the rules frmo the moderator.

Well I guess no one needs lessons :)

some one should post tutors/

--- Renegade v12-06.3 DOS - Alpha Build 001
* Origin: The Titantic BBS Telnet - ttb.slyip.com (1:129/305)

sad when only thing being posted is the rules frmo the
moderator.

i agree... what can you contribute?

)\/(ark


* Origin: (1:3634/12)

sad when only thing being posted is the
rules frmo the moderator.

Well I guess no one needs lessons :)

some one should post tutors/

that's not what the area is/was for... it is for writting pascal code and getting assistance when one has trouble getting things right... rule 1 in the posted rules seems to state that pretty cleanly...

)\/(ark


* Origin: (1:3634/12)

|03Quoting message from |11Mark Lewis |03to |11Tony Master
|03on |1109 Dec 03 17:01:34|03.

sad when only thing being posted is the rules frmo the
moderator.

i agree... what can you contribute?

i don't teach. i learn =]

--- Renegade v12-08.3 Alpha
* Origin: The Titantic BBS Telnet - ttb.slyip.com (1:129/305)

Quoting Tony Master to Scott Adams <=-

sad when only thing being posted is the rules frmo the moderator.

Well I guess no one needs lessons :)

some one should post tutors/

Its better to ask questions and get folks to stay in
the first place. Posting various tutorials don't
do much but to give posts for the echo. Plus
theres many good tutorials out there.

I did a bunch of lessons on IRC once and then later
again on my bbs and echomail network (AdventureNet). After
that I found lots of various tutorials out there.




... AD&D Famous Last Words: "Dragon HORDE? I thought y'said Dragon HOARD!"
--- Fringe BBS
* Origin: EWOG II - The Fringe - 904-733-1721 (1:112/91)

Quoting mark lewis to Tony Master <=-

sad when only thing being posted is the
rules frmo the moderator.

Well I guess no one needs lessons :)

some one should post tutors/

that's not what the area is/was for... it is for writting pascal code
and getting assistance when one has trouble getting things right...
rule 1 in the posted rules seems to state that pretty cleanly...

Yeah in the early '90s this echo was hopping. Then we
got in the mid '90s all the kids needing help with
their school work. Ugh. When I stopped a bit helping
since doing homework/code for someone is not learning
for them. So I changed my helping style to hints
and other methods to learn rather than doing just code.


... "Please relax, its not a bribe." - Londo
--- Fringe BBS
* Origin: EWOG II - The Fringe - 904-733-1721 (1:112/91)

Quoting Tony Master to Mark Lewis <=-

sad when only thing being posted is the rules frmo the
moderator.

i agree... what can you contribute?

i don't teach. i learn =]

So what do ya want to learn?



... "He has no family back home, no on to miss him or fight for his name."
--- Fringe BBS
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|03Quoting message from |11Scott Adams |03to |11Tony Master
|03on |1112 Dec 03 07:01:43|03.

Quoting Tony Master to Mark Lewis <=-

sad when only thing being posted is the rules frmo the
moderator.

i agree... what can you contribute?

i don't teach. i learn =]

So what do ya want to learn?

the best way to learn pointers for now

--- Renegade v12-15.3 - Alpha
* Origin: The Titantic BBS Telnet - ttb.slyip.com (1:129/305)

i don't teach. i learn =]

So what do ya want to learn?

the best way to learn pointers for now

you want to learn the best way to learn pointers or you want to learn pointers by the best way? ;-)

j/k...

i'll see what i can possibly come up with... i'm sure that scott also has something available... maybe he'll post it? my stuff i'll have to input on the fly as we go...

)\/(ark


* Origin: (1:3634/12)

you want to learn the best way to learn pointers or you want to learn point by the best way? ;-)

j/k...

i'll see what i can possibly come up with... i'm sure that scott also has something available... maybe he'll post it? my stuff i'll have to input on fly as we go...

heheh ok cool. pointers for dummies. =]

--- Renegade v12-15.3 - Alpha
* Origin: The Titantic BBS Telnet - ttb.slyip.com (1:129/305)

Quoting Tony Master to Scott Adams <=-

sad when only thing being posted is the rules frmo the moderator.

i agree... what can you contribute?

i don't teach. i learn =]

So what do ya want to learn?

the best way to learn pointers for now

What level of knowledge do you know about them now? I
ask so not to go WAY basic on you :)

I might pull one of my ancient pascal lesson tutorials out
and get the pointer one I did up for ya.

Let me know..



... Babylon 5: A science fiction show that KNOWS where it's going!
--- Fringe BBS
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`07*** Quoting Scott Adams from a message to Tony Master ***`07

Quoting Tony Master to Scott Adams <=-

sad when only thing being posted is the rules frmo the moderator.

i agree... what can you contribute?

i don't teach. i learn =]

So what do ya want to learn?

the best way to learn pointers for now

What level of knowledge do you know about them now? I

Pulled out my old ancient (like 1995!) lessons on pascal. Keep in mind these were in a set of such lessons. I thought the one on pascal was more details but I find its just technical stuff from the language itself. I must've lost the other file with it. But maybe you'll get something out of it? :) Like I say though its 8 years old.


█▓▒░ Pascal Lessons ░▒▓█

o Advanced Topics
■ Lesson 21: Pointers
Pointers are probably th emost difficult to learn in any language.
Pointers in basic terms are just constructs that point to something
in a computer's memory. Think of a map. A street sign is a pointer
which points to a street while addresses point to a particular
slot within that street. Its the same analogy. I will try to
explain the technical part of it but keep in mind something as
short as this lesson can't cover it all. If you need further
aid just ask and I can supply further discussion.
Pointers are used because memory is a tight resource. IF you
have a list of thousands of strings for example its futile and
imposible to keep it flowing as memory will run out. Thus you
should use pointers to point to items in that list. This then
only uses ONE record (of that byte size) instead of the thousnads
of records and their byte size total.
Now for the technicals:

The @ ("at") operator: Pointer operation
▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
You can create a pointer to a variable with the @ operator.

Operator│Operation │Operand types │Result type
═════════╪═════════════════╪══════════════════════╪══════════════════════
@ │Pointer formation│Variable reference, │Pointer (same as nil)
│ │procedure identifier, │
│ │or function identifier│

@ is a unary operator. Special rules apply to use of the @ operator with
a procedural variable.

The type of the value is the same as the type of nil, so it can be
assigned to any pointer variable.

@ with a variable:
Using @ with an ordinary variable (not a parameter) is not complicated.
For example, given these declarations:

type
TwoChar = array[0..1] of Char;
var
Int: Integer;
TwoCharPtr: ^TwoChar;

this statement causes TwoCharPtr to point to Int:
TwoCharPtr := @Int;

TwoCharPtr^ becomes a reinterpretation of the value of Int, as if it were
an array[0..1] of Char.

@ with a value parameter:
Applying @ to a formal value parameter results in a pointer to the stack location containing the actual value.

For example, suppose Fred is a formal value parameter in a procedure and FredPtr is a pointer variable.

If the procedure executes this statement
FredPtr := @Fred;

FredPtr^ references Fred's value.

However, FredPtr^ does not reference Fred itselfit references the value that was taken from Fred and stored on the stack.

@ with a variable parameter:
Applying @ to a formal variable parameter results in a pointer to the actual
parameter (the pointer is taken from the stack).

The type of resulting pointer value is controlled through the $T compiler directive.

For example, suppose the following:
- One is a formal variable parameter of a procedure,
- Two is a variable passed to the procedure as One's actual parameter
- OnePtr is a pointer variable.

If the procedure executes this statement
OnePtr := @One;

OnePtr is a pointer to Two, and OnePtr^ is a reference to Two itself.

@ with a procedure or function:
You can apply @ to a procedure or a function to produce a pointer to its
entry point. Turbo Pascal does not give you a mechanism for using such a pointer.

The only use for a procedure pointer is to pass it to an assembly language routine or to use it in an inline statement.

@ with a method:
You can apply @ to a qualified method identifier to produce a pointer to the method's entry point.

Pointer-type constants
▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
The declaration of a pointer-type constant typically uses a
constant address expression to specify the pointer value.

When you enable the extended syntax (with a {$X+} compiler directive), a
typed constant of type PChar can be initialized with a string constant.

Examples:
type
Direction = (Left, Right, Up, Down);
StringPtr = ^String;
NodePtr = ^Node;
Node = record
Next: NodePtr;
Symbol: StringPtr;
Value: Direction;
end;
const
S1: string[4] = 'DOWN';
S2: string[2] = 'UP';
S3: string[5] = 'RIGHT';
S4: string[4] = 'LEFT';
N1: Node = (Next: nil; Symbol: @S1; Value: Down);
N2: Node = (Next: @N1; Symbol: @S2; Value: Up);
N3: Node = (Next: @N2; Symbol: @S3; Value: Right);
N4: Node = (Next: @N3; Symbol: @S4; Value: Left);
DirectionTable: NodePtr = @N4;

Pointer types
▀▀▀▀▀▀▀▀▀▀▀▀▀▀

A pointer type variable contains the memory address of a dynamic variable of
a specified base type.

You can assign a value to a pointer variable with:
- the New or GetMem procedures
- the @ operator
- the Ptr function

The reserved word nil denotes a pointer constant that does not point to anything.

Pointer:
The predefined type Pointer denotes an untyped pointer (a pointer that does
not point to any specific type).

PChar:
The predefined type PChar denotes a pointer to a null-terminated string.

PChar is declared as:
type PChar = ^Char;

Borland Pascal for Windows supports a set of extended syntax rules
(controlled by the $X compiler directive) to facilitate handling of strings using the PChar type.

Example:
{ Pointer Type Declaration }
type
BytePtr = ^Byte;
WordPtr = ^Word;
IdentPtr = ^IdentRec;
IdentRec = record
Ident: string[15];
RefCount: Word;
Next: IdentPtr;
end;

Don't be worried if you don't understand the above at first.
It will need to sink in with various examples. I can furish
them if needed.



----

Looking it over its not that useful :)


--- Fringe BBS
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|03Quoting message from |11Scott Adams |03to |11Tony Master

What level of knowledge do you know about them now? I
ask so not to go WAY basic on you :)

i know they point to a spot in memory

--- Renegade v01-10.4 DOS
* Origin: The Titantic BBS Telnet - ttb.slyip.com (1:129/305)

Quoting message from Scott Adams to Tony Master

What level of knowledge do you know about them now? I
ask so not to go WAY basic on you :)

i know they point to a spot in memory

You and me both. That is about all I know about them.

chris

--- Renegade v01-10.4 DOS
* Origin: The Titantic BBS Telnet - ttb.slyip.com (1:129/305)

Quoting Tony Master to Scott Adams <=-

What level of knowledge do you know about them now? I
ask so not to go WAY basic on you :)

Well, I have program'd with them in the past and sort of done them right,
but the concept is slightly over my head when it comes to them. Since we have talked last I have went to my libary store and picked up an old novice pascal book that had a few examples and goes over them breifly.

I might pull one of my ancient pascal lesson tutorials out
and get the pointer one I did up for ya.

Let me know..

I see that you postted one. Which is really nice of you. I went ahead and downloaded the message from this bbs and I will go over it and see if I can get a better understanding.

I didn't know about the @ part.

chris

--- Renegade v01-10.4 DOS
* Origin: The Titantic BBS Telnet - ttb.slyip.com (1:129/305)

Hi Tony.

13-Jan-04 00:25:42, Tony Master wrote to Scott Adams

|03Quoting message from |11Scott Adams |03to |11Tony Master

What level of knowledge do you know about them now? I ask so not
to go WAY basic on you :)

i know they point to a spot in memory

The trick is getting them to point to a convenient spot.

there's a number of ways to do that


NIL is a special pointer constant that is used wehn you want a pointer to
point nowhere

@ can be used to point one at an existing variable

new can be used to create an anonymous variable and point a pointer at it

dispose is the opposite of new and deestroys an anonymous variable if you
have a pointer to it



Where it gets interesting is when you make a record that contains a
pointer to a record of the same type.... then you can create a chain of records, of any length and add or remove records at either end or in the
middle of the chain, this is called a linked list.

if you add more pointers to the record you can have a branching chain etc...

Bye <=-

---
* Origin: Don't pay your exorcist & get repossessed! (3:640/1042)

i know they point to a spot in memory

The trick is getting them to point to a convenient spot.

there's a number of ways to do that

NIL is a special pointer constant that is used wehn you want a pointer to
point nowhere

@ can be used to point one at an existing variable

new can be used to create an anonymous variable and point a pointer at it

what about seeing the ^blah?

--- Renegade v01-10.4 DOS
* Origin: The Titantic BBS Telnet - ttb.slyip.com (1:129/305)

Hi Tony.

15-Jan-04 03:37:18, Tony Master wrote to Jasen Betts

new can be used to create an anonymous variable and point a
pointer at it

what about seeing the ^blah?

^blah is the type-name of pointer that points to a blah

blah is usually some sort of record, but you can have simple types too.

Bye <=-

---
* Origin: Bad karma, yea Way bad karma.. (3:640/1042)

Quoting Tony Master to Scott Adams <=-

Quoting message from Scott Adams to Tony Master

What level of knowledge do you know about them now? I
ask so not to go WAY basic on you :)

i know they point to a spot in memory

That's a start :)

Did I post my stupid ancient lesson? :)

I honestly thought I had more detail in it but apparently
didn't. I ought to see if I have my IRC logs when
I taught some stuff on the IRC sysopnet. Might
have something there on pointers.

The basic thing to remember is that pointers can save tons
of memory and free up that annoying 64k data limit. You
can set up a array with a pointer and free up data space.

That is their main purpose in the old world. In modern
world they tend to be more for efficiency since most
compilers use windows and such.



... I no longer have a need to learn. It's part of being an SOB.
--- Fringe BBS
* Origin: EWOG II - The Fringe - 904-733-1721 (1:112/91)

Quoting Chris Hoppman to Scott Adams <=-

Quoting Tony Master to Scott Adams <=-

What level of knowledge do you know about them now? I
ask so not to go WAY basic on you :)

Well, I have program'd with them in the past and sort of done them
right, but the concept is slightly over my head when it comes to them. Since we have talked last I have went to my libary store and picked up
an old novice pascal book that had a few examples and goes over them breifly.

Take a look at the SWAG archives it has a whole section on pointers.
I have a link on my website http://users.cybermax.net/~longshot
on the programming page.

The main rule of thumb is
1) Always open and close pointers. This being critical.
Use the New function to assign memory for the pointer
variable. Using Dispose Function to free up that memory.
In fact if you don't associate 1 New for 1 Dispose it
will cause memory leaks. It can cause problems. If your
program crashes its good to have a ExitProc type procedure
that runs when the program crashes or fails. This will free
up any pointers that aren't disposed. Swag has examples of
all this.
2) Only use pointers if your going to transverse large data sets.
A simple numeric variable of I, J : Integer doesn't need one.
But an array[700,800] of String[70] might find use for them.

Pointers were origianlly invented more or less for use in
B-Trees (Binary trees), Search trees, linked lists using parent
and child nodes (data). Again this is covered in SWAG with
examples.

I might pull one of my ancient pascal lesson tutorials out
and get the pointer one I did up for ya.

Let me know..

I see that you postted one. Which is really nice of you. I went
ahead and downloaded the message from this bbs and I will go over it
and see if I can get a better understanding.

I didn't know about the @ part.

Its about a decade old I think :)...real ancient and not useful
when I look at it today. Back then though it was...
I hardly use the @ part myself. Pascal pointers are far easier
to deal with than C pointers. If you two have problems with
specific questions ask away.

Its 2am so can't give much more brain energy into the posts but
will help you out when I can..



... One more word and you will be part of the excess population - G'kar
--- Fringe BBS
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Quoting Jasen Betts to Tony Master <=-

@MSGID: 3:640/1042 314aecfc
Hi Tony.

13-Jan-04 00:25:42, Tony Master wrote to Scott Adams

Quoting message from Scott Adams to Tony Master

What level of knowledge do you know about them now? I ask so not
to go WAY basic on you :)

i know they point to a spot in memory

The trick is getting them to point to a convenient spot.

there's a number of ways to do that

NIL is a special pointer constant that is used wehn you want a
pointer to point nowhere

@ can be used to point one at an existing variable

new can be used to create an anonymous variable and point a pointer
at it
dispose is the opposite of new and deestroys an anonymous variable if
you have a pointer to it

Where it gets interesting is when you make a record that contains a pointer to a record of the same type.... then you can create a chain
of records, of any length and add or remove records at either end or in the middle of the chain, this is called a linked list.

if you add more pointers to the record you can have a branching chain etc...

Yep. All precursors to the search engines used in most
efficient search systems. B-Trees and all that. Sorts.

Luckilly not had to do a Linked list thing since college :)
Simple today but back then it was like magic :)


... "Besides, I don't think we have the room." - Sheridan
--- Fringe BBS
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