Passing a variable into a function using a reference string.

The simple argument I seek works a little like this—

• Check if variable exists using CHKVAR
• If variable name exists, pass its reference into function

I'm pretty sure what I'm trying to do is comparable to pointing and referencing in C++ (only took a month's worth of CPP in my engineering class, so not too sure). Say I have a set of variables A0,A1,A2, and I need to pass one of them into a function based on the value of N. I don't want to create multiple functions with each having one of the 3 different variables to work on. I want to use a single instance of the function, and so I need to pass a "variable" variable into it. I think I've seen something like this done before, but it's too vague for my memory. Some syntax along the lines of VAR("A"+STR$(N)) (to suit the above example).

DEF FUNC A
REM Do something with A
END
N=0
R=CHKVAR("A"+STR$(N))
IF(R)THEN
 FUNC VAR("A"+STR$(N))
ENDIF

I'm just really at a loss of how this can be done.

EDIT2: There are many ways to do this:

'Passing the value (read only)
FUNC1 VAR("A")
FUNC1 A 'same

DEF FUNC1 V
 PRINT V
 V=3 'DOES NOT WORK
END

'passing the name (only works with global variables)
FUNC2 "A"

DEF FUNC2 V$
 PRINT VAR(V$)
 VAR(V$)=3
END

'input and output (works with anything)
FUNC3 VAR("A") OUT VAR("A")
FUNC3 A OUT A 'same
VAR("A")=FUNC3(VAR("A")) 'same
A=FUNC3(A) 'same

DEF FUNC3 V_IN OUT V
 V=V_IN 'get value
 PRINT V
 V=3
END

'using arrays to cheat:
'(arrays are passed as reference type always, so changing an array inside a function will change the real array, unlike with number variables)
DIM A[1]
FUNC4 VAR("A")
FUNC4 A 'same

DEF FUNC4 V[]
 PRINT V[0]
 V[0]=3
END

You can't create new variables, so if you need to store more data you'll have to use arrays.