(03-11-2021, 11:13 PM)georgeo Wrote: Actually, my question is more related to subroutines than functions. So, is the following code valid:
---with variables labelled 'n' in both the main program and the subroutine.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
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