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Sanjay Minni wrote:
> My son (11-12 yrs) wants to learn Smalltalk
> No merits, no syllabus, no recommendations
> - just fate (he sees me battling it and he did a bit of LOGO)
>
> 1. I have a copy of Dolphin4 PRO
> 2. I am not proficient in ST at all
> (but otherwise a seasoned programmer)
>
> How to go about it or to abandon it ?
Second part first - if you want to abandon it, do it NOW.
This stuff is extraordinarily addictive.
No? Still interested? Ok - here goes...
Imagine that instead of the entire LOGO environment
having direct access to the turtle graphics routines,
those routines are completely encapsulated in, and
known only to, this one thing called 'turtle'.
In other words, 'turtle' is an object.
You are used to specifying graphics routines
something like this:
do penDown().
do forward(2).
do rotate(90).
etc...
You tell the system to 'do' a 'procedure',
then another, etc.
Now, if you had the aforementioned 'turtle' object,
you would instead program it thus:
turtle penDown.
turtle forward: 2.
turtle rotate: 90.
etc...
You send a message to the turtle object,
telling it what to do.
That's the motivational set up - now for a place to start.
Fire up Dolphin, and figure out which of the windows
is a 'workspace'. If there isn't one, hunt around in
the menus until you find something that sounds like it
might create a workspace, and create one.
Type this as a line, somewhere in the workspace:
'Sanjay Minni'
Now, with the cursor on that line, right click,
and select 'inspect it'. You'll get a new window
showing you that the object on that line is a string.
Dismiss the window.
Change that line so it looks like this:
'Sanjay Minni' inspect
With the cursor on that line, right click,
and select 'evaluate it'. You'll get the same
thing as before, because when you evaluate that
line, the message 'inspect' gets sent to the
receiver (an object), which is a string.
The string knows what that message means.
When you selected 'inspect it', you caused
an #inspect message to be sent to the object
on the line; when you selected 'evaluate it'
you caused a #compileAndExecuteYourself
message to be sent to the object on line.
[Note - not really true, but virtually true].
Ok, now change that line to look like this:
'Sanjay Minni' includes: $a
Put your cursor on the line, and evaluate it.
Hmmmm, nothing happened.
Put your cursor on that line again, but this
time select 'display it'. The word 'true'
will be added to the line. Why?
Well, 'display it' really means
'first evaluate it, then print the result'.
The code is understood like this:
Send the message 'includes: $a'
to the string 'Sanjay Minni'.
In other words, ask the string
whether it includes the character a.
{ The string responds -- true. }
The first time, we said 'evaluate it'.
So the message was sent, and responded to.
But we couldn't see the response - it was
no longer needed for anything and so it was
thrown away; i.e. it was garbage, and the
garbage collector found it, and got rid of
it for us.
The second time, we said 'display it'.
So the message was sent, and responded to.
And the response was printed. After which,
it was no longer needed for anything and so
it was thrown away.
Ok, so you get the idea.
You can open up some other windows,
to browse the system in various ways.
You can learn a lot by doing so.
Reading the tutorials on the Dolphin
web site will help too.
For a little help in translating what
you know into Smalltalk form, google for
'Reading Smalltalk'.
For help with the 'tone' of the language,
find the song "Alice's Restaurant" by Arlo Guthrie.
As a final hint as to where you're headed,
change that original line to look like this:
'Sanjay Minni' reverse collect: [:ch| ch asUppercase]
Put your cursor on that line, and either inspect it,
or display it. Have your son explain what happened.
Regards,
-cstb
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