Unless I have made a mistake,  it appears as if a special variable is not a
global variable (meaning that the variable can be seen by any module and
changed by any module so that its value is always the value last defined).

In my example, I defined a special variable($C=2) then called a module (no
parameters passed). I read the special variable within the called
module($C=5). Changed that special variable (originally had the value of 2,
but now defined it as 5), then returned from the called module. Upon return
I looked at the value of the special character. its value, newly defined
within the called module(5), did not persist but retained the value it
originally had(2) before the call to the module.

Interpretation of the results imply that special variables are defined at
compile time and not dynamically.

I thought, that  special variables were dynamically assigned and hence have
the attributes of a global variable defined by me in the first paragraph.

I must have a misunderstanding. please help me understand.

bil

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can you show some code ?

$  Runsun Pan, PhD

$ libs: doctest , faces ( git ), offline doc ( git ),runscad.py( 1 , 2 , git );

$ tips: hash( 1 , 2 ), sweep , var , lerp , animGif

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I would love to show some code....but I am not sure how to attach the code
here.  Do people prefer to "embed" (I am assuming if i point to a file in
Embed, the file contents will appear in this box), or link the file to this
box. not sure what linking will actually do.  tell me what you want and how
and i will gladly respond

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copy and paste ?

$  Runsun Pan, PhD

$ libs: doctest , faces ( git ), offline doc ( git ),runscad.py( 1 , 2 , git );

$ tips: hash( 1 , 2 ), sweep , var , lerp , animGif

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module a(b)
{  echo ("enterred module a");

// initial conditions for module
     echo ("b, passed parameter value arriving within module a(), is

defined as = ", b);
echo ("special variable value before module a() code executed $C =
", $C);

// changing passed parameter 
     echo ("just before I change passed parameter");
     $D = b;  // simple change to test concept
     echo (" passed parameter b which shall be changed $D =" ,  $D);
     $D = b + 50;
     echo ("changed passed parameter $D = ", $D);

// changing global value
     $C = 5;
      echo ("special variable value created outside of module a() but

changed within module a() $C = ", $C);
};

// TESTING MODULE a()
//  Defining special variables prior to module a() call
$C = 2;  //define a special variables prior to call to module
(a)
echo ( "before call to module a(), special variable,  $C was
defined as", $C);

 //  Defining parameter to be passed to module a
       b = 2; 
       echo ("before call to module a(b), b parameter to be passed was

defined as",b);

//  Call to module a()
      a(b);     

//  Return from module a() 
       echo ("returned from module a()");
       echo ("upon return from module a() value of passed parameter b =

",b);    //expect b to have original passed value
echo ("upon return from module a() value of special variable $C
=", $C); // expect special variable defined external to module a() to have
been changed by module a()
echo ("upon return from module a() value of special variable $D=
", $D);  // expect special variable created within module a() to be seen
external to module a()

/* INTERPRETATIONS OF EXPERIMENT
(1) special variable $C, does not act as a global variable.
$C, created and defined before call to module a() is redefined in
module a(). The change does not make it out of module a().
(2)  special variable $D does not act as a global variable.
$D, created and defined within module a() is not considered
defined outside of module a()
(3) Thus my interpretation of special value is that special values
allow an external (to a module) constant be seen internal to a module but it
can not be changed within the module and the outside world knows about the
change.
*/

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