Understanding scope of variables

[boriel]

Actually, my question is more related to subroutines than functions. So, is the following code valid:

Code:

sub myFunction( byref total as uinteger, name$ as string )     dim length, n as ubyte     length = len(name$)     if length=0 then return     end if     for n = 0 to length-1 total = total + code(name$(n))     next n         return end sub REM Main program dim n as ubyte dim total as uinteger n = 14 myFunction(total, "Hello") print "Answer = " + str$(total) print "n = " + str$(n) stop

---with variables labelled 'n' in both the main program and the subroutine.

Thanks again

Both SUB and FUNCTIONS are the same (with the small difference that FUNCTIONS are expected to return a value).
When you DIM a variable within a function or sub, it's a *local* variable, and will be used only in that scope and destroyed upon exiting that scope. If there's another variable with the same name in an outer scope (i.e. the global one) this variable is "shadowed" by the LOCAL one and not accessible. So your program is OK (and use a Function, it's also OK.

If you don't use DIM within a FUNCTION / SUB, the global variable will be used *if already declared*. If it's not declared, an implicit local variable is then created (which again is destroyed upon exiting). If you don't want this to happen, compile with --explicit, which will require every variable to be declared with DIM before use.

This is very counterintuitive:

Code:

SUB test1() n = n + 1 ' Declares a local variable n, there's no previous n declared PRINT n END SUB DIM n as UByte = 3 SUB test2() n = n + 1 ' Uses n from the global scope because there's one already declard PRINT n END SUB SUB test3() DIM n = 5 n = n + 1 ' Uses n from the local scope because it's declared PRINT n END SUB test1 test2 test3

So to avoid test1() to implicitly declare a local var, compile with --explicit