Global vars

[compsystems]

Hi, how can I save global variables, but when I run a program call again, these again do not lose their content

Thanks

[parisse]

I don't understand what you mean.

[compsystems]

solved by putting x: = 0 before the definition of the function.
but the compiler should detect that the x variable has been defined previously and not throw the warning message Warning: x, declared as global variable(s)

Code : Tout sélectionner

x:=0;

f():={
  x:=x+1; // global
  print(x);
}:;

// Parsing f
// Warning: x, declared as global variable(s) ...
// compiling f

f() [enter] returns 1
f() [enter] returns 2
f() [enter] returns 3

now

Code : Tout sélectionner

f1():={
  y:=y+1;
  print(y);
}:;

// Parsing f1
// Warning: y, declared as global variable(s). If symbolic variables are required, declare them as local and run purge
// compiling f1

f1() [enter]
"y: recursive definition Error: Bad Argument Value"

the trick for the variable to be symbolic is to add the following statement
local y; purge(y);

Code : Tout sélectionner

f1():={
  local y; purge(y);
  y:=y+1;
  print(y);
}:;

f1() [enter] y+1

but to be more explicit the code, I think that a new command is necessary Symbs id0,id2,...idn it's a great idea?

Symbs y; replaces local y; purge(y);

Code : Tout sélectionner

f1():={
  Symbs y;
  y:=y+1;
  print(y);
}:;

f1() [enter] y+1

Code : Tout sélectionner

x:=0; // global
f():={
  x:=x+1;
  print(x);
}:;

f1():={
  local y; purge(y); // Symbs y
  y:=y+1;
  print(y);
}:;

f2():={
  local x; purge(x); // Symbs x
  x:=x+1;
  print(x);
}:;

f();f1();f2(); [enter]
1, y+1, x+1

f();f1();f2(); [enter]
2, y+1, x+1

f();f1();f2(); [enter]
3, y+1, x+1

[parisse]

solved by putting x: = 0 before the definition of the function.
but the compiler should detect that the x variable has been defined previously and not throw the warning message Warning: x, declared as global variable(s)

First the compiler should not check that x is assigned, because that may change later, second it is essential to throw a warning message, because functions should not use global variables, only local variables. Global variables are tolerable for symbolic variables, but it's better to use a symbolic local variable, as explained in the warning. If you really want a global variable, you can still declare it as global.

[compsystems]

ok,

What do you think of an alternative command

local y; purge(y);
as
symbs y;

local y,z; purge(y,z); as symbs y,z;

other CAS as the matlab symbolic toolbox follows this syntax

[parisse]

Don't forget that it's easy to make suggestions, but it's not as easy to implement them and I have limited ressources, I can not spend one or 2 hours per day implementing all your suggestions. So please try to sort your suggestions, and send only important ones, for example replacing local y; purge(y); by whatever y; is not very important since the functionnality is already available. The same applies for cosmetic UI changes.

[frederic han]

NB, there are several way to do this.

for instance in giac simple quotes means the unevaluated form of the object (it is not the same as double quotes) so I often do this:

Code : Tout sélectionner

f1():={
  local y:='y';
  y:=y+1;
  print(y);
}:;

another way to do this:

Code : Tout sélectionner

f1():={
  local y; purge(y);
  y:=y+1;
  print(y);
}:;