A newbie needs some help in squeak (maths, algorithm and drawing)

Hello,
I have to realize an application in squeak which is an icon generator. My questions are the following:
I have an algorithm which describe a spiral and i'd like to transcript it into squeak, but it doesn't work.
The original algorithm is:
" for( i=0; i < len; i++ ) {
  theta = 2*pi*float(i) / ppr;
  r = 0.15 * sqrt(theta);
  x = r * cos(theta);
  y = r * sin(theta);
  }
"

And what i've done but that doesn't work:
"
spiral: len with: ppr

        | theta r x y |
       
        0 to: (len-1) do:
                [:i | theta = 2* Float pi * i / ppr.
                        r = 0.15 * (self sqrt: theta).
                        x = r * ( self cos: theta).
                        y = r * ( self sin: theta).
                ]
"

But this code doesn't work and I don't know how to code my spiral algorithm and how it will be displayed on screen when running.
Thank you for your help.
Chris

2007/4/26, Christophe Bouchard <[hidden email]>:
What are (self sqrt:), (self cos:) and (self sin:)? Don't you mean:

spiral: len with: ppr
       | theta r x y |

       0 to: (len-1) do:
               [:i | theta = 2* Float pi * i / ppr.
                       r = 0.15 * theta sqrt.
                       x = r * theta cos.
                       y = r * theta sin.
               ]

It still won't print anything to the screen however.

--
Damien Cassou

On Apr 26, 2007, at 16:26 , Christophe Bouchard wrote:

Check out classes Scanner, Parser, and Compiler to find out about  
assignment.

Now, on the newbies list, they might have told you to use ":=".

http://lists.squeakfoundation.org/mailman/listinfo/beginners


- Bert -

2007/4/26, Bert Freudenberg <[hidden email]>:
> Now, on the newbies list, they might have told you to use ":=".

Good catch

--
Damien Cassou

El 4/26/07 11:26 AM, "Christophe Bouchard"
<[hidden email]> escribió:

> But this code doesn't work and I don't know how to code my spiral algorithm
> and how it will be displayed on screen when running.
> Thank you for your help.
> Chris
"Draw a spiral with a pen that is 2 pixels wide."
    "Display restoreAfter: [Pen example]"

Hello Chris,

>> But this code doesn't work and I don't know how to code my spiral algorithm
>> and how it will be displayed on screen when running.
>> Thank you for your help.
>> Chris
EJDC> "Draw a spiral with a pen that is 2 pixels wide."
EJDC>     "Display restoreAfter: [Pen example]"

don't know how much a newbie you are, what Edgar is saying here
translates to:

"Open a Browser, find class pen, switch to the class side and read the
class method named example."

This code also draws the spiral to the screen.


Cheers,

Herbert                            mailto:[hidden email]

Perhaps something more like this...


        | theta r pen p|
        pen _ Pen new.
        len _ 200.
        ppr _ 10.
        0 to: (len-1) do: [:i |
                theta _ 2 * Float pi * i / len * ppr.
                r _  i.
                p _ r * theta cos @ (r * theta sin).
                pen goto: p + Display boundingBox center]


I'm not sure what len and ppr mean to you though!

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of
Christophe Bouchard
Sent: 26 April 2007 3:27 pm
To: [hidden email]
Subject: A newbie needs some help in squeak (maths, algorithm and drawing)


Hello,
I have to realize an application in squeak which is an icon generator. My
questions are the following: I have an algorithm which describe a spiral and
i'd like to transcript it into squeak, but it doesn't work. The original
algorithm is: " for( i=0; i < len; i++ ) {
  theta = 2*pi*float(i) / ppr;
  r = 0.15 * sqrt(theta);
  x = r * cos(theta);
  y = r * sin(theta);
  }
"

And what i've done but that doesn't work:
"
spiral: len with: ppr

        | theta r x y |
       
        0 to: (len-1) do:
                [:i | theta = 2* Float pi * i / ppr.
                        r = 0.15 * (self sqrt: theta).
                        x = r * ( self cos: theta).
                        y = r * ( self sin: theta).
                ]
"

But this code doesn't work and I don't know how to code my spiral algorithm
and how it will be displayed on screen when running. Thank you for your
help. Chris

2007/4/26, Gary Chambers <[hidden email]>:
with ':=' when you see '_' :-)

--
Damien Cassou

Of course. Cut and pasted from workspace (the code saves as ":=", naturally
;-)

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Damien
Cassou
Sent: 26 April 2007 6:07 pm
To: The general-purpose Squeak developers list
Subject: Re: A newbie needs some help in squeak (maths,algorithm and
drawing)


2007/4/26, Gary Chambers <[hidden email]>:
with ':=' when you see '_' :-)

--
Damien Cassou

On Thursday 26 April 2007 7:56 pm, Christophe Bouchard wrote: I am not sure what ppr means, but theta calculation doesn't appear right.
Here is an example that you can type into Workspace and run:

turns := 3.
radius := 90.
points := 30.
p := Pen new down.
middle := p location.

0 to: (turns-1) do: [ :n |
        1 to: points do: [ :i |
                theta := 2.0 * Float pi * i / points.
                r := radius * (n + (theta/(2.0*Float pi))).
                x := r * theta cos.
                y := r * theta sin.
                p goto: (middle + (x @ y)). ] ]

BTW, in Squeak,the convention is to think of spiral from the pen's
viewpoint and compute steps and turns. For a spiral, the pen would move
forward by increasing amounts for every turn, so the logic becomes:

n := radius/points.
angle := 360/points.
s := n.
1 to: turns do: [ :t |
        1 to: points do: [ :i |
                p go: s; turn: angle.
                s := s + n ] ].


Hope this helps .. Subbu