25.1.3 Local variables
Local variables in a function definition can be given initial values
in the line they are declared in by putting their initialization in
parentheses; for example,
is the same as
Local variables should be given values within the function definition.
If you want to use a local variable as a symbolic variable, then you
can indicate that with the assume command
(see Section 3.3.8). For
example, if you define a function myroots by
| myroots (a):={
local x;
return solve(x^2=a,x);
} |
then calling
will simply return the empty list. You could leave x
undeclared, but that would make x a global variable and could
interact with other functions in unexpected ways. You can get the
behavior you probably expected by explicitly assuming x to be a
symbol;
| myroots(a):={
local x;
assume(x,symbol);
return solve(x^2=a,x);
} |
(Alternatively, you could use purge(x) instead
of assume(x,symbol).) Now if you enter
you will get