How do you assign a global var in a CAS function?

[parisse]

You can assign variables in a local statement, but you must take care of priorities, for example

Code:

local a:=1,c:=3;

will assign a to 1,3 like

Code:

local a:=(1,c:=3);

unlike

Code:

local (a:=1),(c:=3);

That's why it is recommended to assign local variables outside of the local declaration.
In a CAS program, non declared variables are global, if they already exist in Home (i.e. you made an EXPORT before) then they are HOME variables, otherwise they are global CAS variables.