Declaring Arrays as Function Parameters

[Andrew Burt]

Can someone please clarify the purpose of MIN and MAX
when declaring array parameters in a Function? I've used VB and
QB extensively in the past and the use of MIN and MAX seems a
bit alien to me.

Is its use optional? For instance, if I have an array declared
as below:

DIM MyList(1 TO 30) AS INTEGER

Can I define my function as follows:

DECLARE FindAverage (TheList())
.
.
FUNCTION FindAverage TheList() AS INTEGER

or must I define the function as:

FUNCTION FindAverage TheList(MIN, 1) AS INTEGER




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[Lance Edmonds]

Generally this strategy is used in PBU code, rather than in the main code. Additionally, the MIN/MAX keywords are used in the DIM statement, not the sub/function prototype.

Anyway, here is a brief example of the usage. See page 92 in the Refernce Guide for a description of the differences between MIN and MAX in a DIM statement.

DIM a(100:200) AS SHARED LONG
CALL mysub
PRINT a(100), a(200)
END
 
SUB MySub
 DIM a(MIN,1) AS SHARED LONG
 PRINT LBOUND(a(1)), UBOUND(a(1))
 a(100) = 1
 a(200) = 2
END SUB

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Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Andrew Burt]

Thanks for your response. The use of MIN|MAX in a DIM statement
makes sense. What is muddying the water a bit is the way that
the Reference Guide shows that array parameters for functions
must be declared using MIN|MAX (page 128). Theoretically,
several difference arrays may be passed to the same function in
various places in a program and these arrays don't always have
to have the same upper and lower bounds. Having to specify in
the function prototype if the array's lower bound is zero could
present problems.

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[Michael Mattias]

Using the internal function ArrayInfo&, you can pass ANY type of array to a procedure, get its type and your procedure can act accordingly.

You have to call the procedure passing the address of the array descriptor, as in...

 DIM pDescriptor AS DWORD

  pDescriptor = VARPTR32 (array())

FUNCTION PlayWithArray (BYVAL dAddr AS DWORD)

' use ArrayInfo& here to get the type of data in the array.

   
END FUNCTION

ArrayInfo& is documented in the PB/DOS help file under 'internal functions'.

(It is also not available in PB/Windows, a real shame)

If you need a more complete sample, let me know. I have some code I will send you or if I'm in a good mood I'll post it in the source code forum.


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Michael Mattias
Racine WI USA
[email protected]