...

If my understanding is right then you cannot send a message to an object passed as a parameter to a method of another class.

Why not show us a sample of what you mean.

Okay :-)

class B anotherMethod: self doSomething:

class A aMethod: aParam aParam anotherMethod:

That is probably not legal SmallTalk from what I understand on the VM ?

Or are method names unique ?

Aaron

On Sun, Dec 05, 2004 at 05:20:31AM -0000, Aaron Gray wrote:

...

...

If my understanding is right then you cannot send a message to an object passed as a parameter to a method of another class.

Why not show us a sample of what you mean.

Okay :-)

class B
    anotherMethod:
        self doSomething:

class A
    aMethod: aParam
        aParam anotherMethod:

That is probably not legal SmallTalk from what I understand on the VM ?

Or are method names unique ?

Hi Aaron,

Please try the following. It will take you about a half hour to do this the first time, but I think you will be glad to have spent the time once you have done it.

Make a new project:

world menu -> open... -> morphic project

The new project will appear as a box with a label like "Unnamed2". Click on the box to enter the project.

Open a browser and a workspace. Click on Tools flap (on the right side of the screen). Use the mouse to drag a Browser onto your screen, then do the same for a Workspace (you can also create these using the world menu -> open...).

In your browser, experiment with your mouse buttons to see what they do. On my computer (Linux), the left button selects things, middle button brings up menus, and right button brings up the "Morphic halos" (little buttons around the Morphs that make up your browser). On Windows, the right button does the menu things, but I'll just refer to "middle button" in what follows.

Make a new class category called "My Junk". In the upper left pane of the browser (the one with the list of Kernel-Objects, Kernel-Classes, etc), middle button click for menu, then "add item...". In the category name prompt that comes up, type "My Junk", then click Accept.

Now in the large bottom pane of the browser, you can create your new class. Where it now says "Object subclass: #NameOfSubclass", change it to say "Object subclass: #MyTestClassB", then accept the text to create the class. You can accept the text with keyboard <alt>s, or middle button click and "select" from the menu.

MyTestClassB will show up in the second-from-left pane in the browser. Underneath this, click the "?" button. The class comment entry area appears in the bottom pane. Replace the text with a comment such as "This is my test class B." Accept the text. (I'm just telling you this part so you will be in the habit of doing it. Think of it as a note to yourself explaining why you created the class, just in case you need to remember it six months from now.)

Now click on the third-from-left pane, the one that says "no messages". Do middle button click, then select "new category...". Select "new...", then enter "my test methods" as your catagory. (Again, this is just to get in the habit of putting things in categories that will mean something to you six months from now).

Now you can enter a method. In the bottom pane, there is some example text that suggests the layout of the method source code. Replace this with your actual method, then accept it. Your actual method can look like this (the underscore character will be a left-arrow when you type it into Squeak):

anotherMethod: aParameter "This method does something with aParameter, but for now it will just halt so I can see it in a debugger." | myTempVar | myTempVar _ aParameter. self halt. "self doSomething might go here" ^ myTempVar

Now you have your class B. You can give it a #doSomething: method also if you want to have your #anotherMethod do a "self doSomething: aParam"

Now make another class called MyTestClassB. Give it a method like this:

aMethod: aParam "This method does something with aParam"

| myFirstTempVar | myFirstTempVar _ aParam. self halt. ^ myFirstTempVar

Now you can experiment and see how things really work. Go to your workspace (the white window), and enter the following to get started:

anInstanceOfB _ MyTestClassB new. anInstanceOfA _ MyTestClassA new. anInstanceOfB anotherMethod: anInstanceOfA.

Accept this text in the workspace (<alt>s), then highlight it with the mouse. Middle button click, and select "inspect it".

Your code will start running, and stop with a red "Halt" dialog when it reaches a "self halt" in your code. Click the "Debug" button to go into the debugger and see what is happening. (Note: You can also run code in the debugger just by putting a "self halt" in the text on the workspace, right before the code you want to evaluate).

In the top pane of the debugger, you will see levels of the execution stack. Click on the second from the top, where you see the "myTestClassB>>anotherMethod:", and you will now see your source code in the middle pane.

In the lower right debugger pane, enter the text "myTempVar aMethod: self". Highlight your text, then middle button click, and "Inspect" it. You will get another halt dialog to put you into another debugger, which will show the result of sending your instance of MyTestClassB as a parameter for the #aMethod message sent to MyTestClassA.

Now it's time to start exploring and experimenting. I won't try to explain how to use the debugger, just start clicking on things and see what's what. You have experience with other languages, so it will probably make sense to you right away. Smalltalk is a stack oriented virtual machine, so it should look familiar if you have worked with Java or anything similar. Just click on levels of the stack (top debugger pane) and experiment to your heart's content with the things in the other debugger panes. Try clicking on things, double clicking on things, and middle button click to see menu options.

You can do *anything* you want right in the debugger, including change your code and proceeding. You can inspect variables and parameters, you can send messages to them, you can see exactly with is "visible" at any point in the execution, and so forth. Try treating the panes at the bottom as little interactive workspaces, and if you want to modify any of the code you are experimenting with, do it right in the big middle code pane.

Have fun,

Dave

p.s. One last thing that might interest you: Go back to your Browser and click on one of your methods so you can see the source code. In the middle of the browser is a row of buttons, click on the one on the far right labelled "source". In the "What to show" dialog, select "byteCodes". Now you are looking at the stuff that matters to the virtual machine.

Does your Browser look similar to the attached? (sorry for the 13k png ...)

On December 5, 2004 04:06 pm, Aaron Gray wrote:

Okay sorry I have been away for a while.

...

Now you can enter a method. In the bottom pane, there is some example text that suggests the layout of the method source code. Replace this with your actual method, then accept it. Your actual method can look like this (the underscore character will be a left-arrow when you type it into Squeak):

anotherMethod: aParameter "This method does something with aParameter, but for now it will just halt so I can see it in a debugger."

| myTempVar |

myTempVar _ aParameter. self halt. "self doSomething might go here" ^ myTempVar

I am getting to this point and the method compiler is responding saying "Argument name expected ->"

Argument name expected ->anotherMethod: aParameter "This method does something with aParameter, but for now it will just halt so I can see it in a debugger."

| myTempVar |

myTempVar _ aParameter. self halt. "self doSomething might go here" ^ myTempVar

What am I doing wrong ?

Aaron

"Aaron Gray" angray@beeb.net wrote:

I also am finding that I do something in the workspace once and it does not work then doing it again and it does with no obvious difference that I can determine right now, maybe with a bit more experience I will see why.

Aaron

One thing worth knowing is that if you do not declare your temporaries in a workspace they will be created as bindings in the workspace, and thus "survive" for later code snippets.

That is the only thing I know that could cause the "same" code to behave differently the next time. Disregarding state in globals of course. :)

regards, Göran

Le 2004/12/05, Aaron Gray angray@beeb.net écrivait :

Yes, but it was not Accepting it for some reason, but now it is working fine, retried again and it was fine, so I do not know what I was doing wrong.

Hi Aaron, I think you inadvertently hit the 'uppercase' key of your keyboard...is it possible? I noted that on Windows when I can't accept code it is that I'm in uppercase. (wondering the exact term....I don't talk about 'shift' key but the one above it)...

Raymond

David,

Its working now, do not know why, but I have tried it again for a new class and it works fine so I do not know what I was doing wrong to get the message "Argument name expected ->" before the method name.

Aaron

Good, that will give you something to experiment with. I can tell from your earlier posts that you have some experience with other languages, so I think you will find Squeak quite interesting once you start poking around in the debugger and tinkering with the gears and levers.

Thanks for the introduction,

Aaron

Hi,

start to read Smalltalk by Example available as free books on my web page....

Okay will do soon, I was going to read the SmallTalk language definition when I get round to it. Maybe I will buy SmallTalk by Example as I do prefer books compared to online reading. Thanks, I will have a look at it online first.

Online Free Books at http://www.iam.unibe.ch/~ducasse/WebPages/FreeBooks.html

BTW: You gave me an old redirected URL !

Many thanks, I was sort of waiting for that advice.

Aaron

Ack - pretty please Aaron, try to remember there's no capital T in Smalltalk. A trivial point I suppose but it does grate somewhat to read after so many years.

Sorry, force of habit after writing all those variable names :)

Smalltalk Smalltalk Smalltalk

There that's better :-)

Aaron

On Mon, 06 Dec 2004 15:08:52 -0800, Tim Rowledge tim@sumeru.stanford.edu wrote:

Ack - pretty please Aaron, try to remember there's no capital T in Smalltalk. A trivial point I suppose but it does grate somewhat to read after so many years.

Shouldn't it be "smallTalk"?<s>

Hi stéphane,

start to read Smalltalk by Example available as free books on my web page.... Online Free Books at http://www.iam.unibe.ch/~ducasse/WebPages/FreeBooks.html

Sorry, but where is the index ?

The introduction to the book says it has a good index, but there seems to be no index ?

Aaron

But I could not recreate the index...too bad. I also have something else to do.

In the actual new release of the book, there is a problem with the index of the pdf file. Indeed, you have to get look at the sub-index to see chapter titles. I agree that it's so painful that I prefer to use the oldest release...

Cheers, Houssam ____ "Le paradis touche les pieds des mères..."

...

...

...

http://csl.ensm-douai.fr/fakih

-----Message d'origine----- De : squeak-dev-bounces@lists.squeakfoundation.org [mailto:squeak-dev-bounces@lists.squeakfoundation.org] De la part de Aaron Gray Envoyé : mardi 7 décembre 2004 17:50 À : The general-purpose Squeak developers list Objet : Re: Smalltalk language - Smalltalk by Example

Hi stéphane,

...

start to read Smalltalk by Example available as free books on my web page.... Online Free Books at http://www.iam.unibe.ch/~ducasse/WebPages/FreeBooks.html

Sorry, but where is the index ?

The introduction to the book says it has a good index, but there seems to be no index ?

Aaron

...

If my understanding is right then you cannot send a message to an object passed as a parameter to a method of another class.

Is this correct ?

No, you can do this. (If I understand you correctly.) In fact, there are probably thousands of methods in Squeak that do this. :-)

Right, I need a good language introduction then. Any suggestions ?

I obviously have alot more to learn about the System-Compiler and VM

Aaron

...

Right, I need a good language introduction then. Any suggestions ?

I obviously have alot more to learn about the System-Compiler and VM

Aaron

Why?

I have been studying Virtual Machines and Compiler technologies and have only been looking at SmallTalk for three days so far so forgive my lack of knowledge of SmallTalk and Squeak. I should have read more first and studied the SmallTalk properly before hand and I may have not posed such a silly question !

You can work an entire career in Smalltalk without ever having to do anything directly with the System-Compiler or the VM.

Indeed, I would venture a guess that the vast majority of readers of this list never venture into that territory.

Yep.

Sorry for any disturbance,

Aaron