Variables in function declarations

[Paul Harness]

Thank you all for your input. On this function, I am willing
to pay the cost of run time conversion between data types.

I have actually used PB for all of my programming experience,
except some c++ at school and for windows.

I ended up writing the function with the byval in the function
declaration, and it works great. I had tried bycopy, but that is
for the function call.

Anyway, thanks again.

PS, these forums are great. So many ideas and examples.

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[Michael Mattias]

UNION AnyDataType
 L   AS LONG
 EX  AS EXT
 S   AS SINGLE
 I   AS INTEGER
 DW  AS DWORD
 ...
END UNION


FUNCTION AcceptMePlease (WhatType AS LONG, Z AS AnyDataType) AS LONG

  SELECT CASE WhatType
    CASE  %TYPE_LONG
      CALL Processlong(Z.L)
    CASE  %TYPE_SINGLE
      CALL ProcessSingle (Z.s)
    CASE %TYPE_INTEGER
      CALL ProcessInteger (Z.I)
    yadda yadda
   END SELECT
END FUNCTION

With CC/3 and Win/7, you can also pass a one-element array in lieu of a UNION and use the ARRAYATTR function to get the datatype. (hmm, come to think of it, PB/DOS's ArrayInfo& function will also tell you the datatype).

MCM


[This message has been edited by Michael Mattias (edited December 14, 2002).]

[Tom Hanlin]

EXT will encompass most numeric types just fine but, it's useful to know
that functions don't accept generic types by default because there can be
side-effects involved in morphing the parameter types and, it's grossly
inefficient to have to change types on the fly. Otherwise, there would be
no need to ask this kind of question.

Possibly, you're used to dealing with a medium-late version of Visual Basic,
or one of the dBase-style languages that pretend there's no such thing as a
data type. That can be convenient, but you pay a heavy price for the works
behind the scenes, and PowerBASIC doesn't hide that tax from you.

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Tom Hanlin
PowerBASIC Staff

[Paul Harness]

Thank you very much. I had tried BYCOPY in the declaration, but
that didn't work. The BYVAL and the EXT is exactly what I was
looking for.

THanks,

Paul


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You can use AS EXT. For example, the function below accepts passing any kind of numeric variable.

FUNCTION DS_FixedRound(BYVAL xNum AS EXT) AS CUX
   FUNCTION = ROUND(xNum + 0.005 * SGN(xNum), 2)
END FUNCTION

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[This message has been edited by JOSE ROCA (edited December 13, 2002).]

[Paul Harness]

Hello all, I greatly appreciate these forums, I have learned a
great deal.

However, does anybody know how to declare a function so that it
will accept more than one type of variable?

I have written a function to create a hex string out of a number,
(I wrote one instead of the PB function because I need it to
return the leading zeros as appropriate.) Anyway, I would like
to be able to just pass it ints, words, longs, ... without the
bycopy statement? I guess it is mostly a personal irritation, but
I am looking for ideas.

Thanks guys,

Paul Harness

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