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> From: H. v. L. [mailto:hvl{([at]})nowhere.xy
> On Mon, 13 Dec 2004 16:55:47 +1030, CFB Software <info{([at]})nowhere.xy
> wrote:
>
> > The built-in function LEN in BlackBox accepts a type T as an actual
> > parameter as well as a variable of type T.
>
> > Is the acceptance of a typename as a parameter intentional or an
> > accident?
>
> In my opinion this is not an accident.
> With one exception, added in BB 1.4 and not existing in Oberon or
> BB 1.3,
> LEN always returns the length of the type, be the parameter a type or a
> variable.
> The exception of course is the explicit reference to a variable via the
> $ operator which moreover must be a string variable.
> All this seems to indicate that originally the type was meant and the
> possibility of a variable was added for convenience.
>
>
Thank you for reminding me that LEN was part of Oberon - I was thinking that
it was introduced during the evolution to Component Pascal.
I've just tried it out on the Win32 ETH Oberon compiler and it unambiguously
rejects a type name as a parameter to LEN with the error message:
"This expression must not be a type or procedure"
However, there are subtle differences between the two language reports:
ETH Oberon-2:
=============
Name - LEN(v, n)
Argument type - v: array; n: integer const.
Result type - LONGINT
Function - length of v in dimension n (first dimension = 0)
Name - LEN(v)
Argument type - v: array <-----------<<<
Result type - LONGINT
Function - equivalent to LEN(v, 0)
OmS Component Pascal:
=====================
Name - LEN(v, x)
Argument type - v: array; x: integer constant
Result type - INTEGER
Function - length of v in dimension x (first dimension = 0)
Name - LEN(v)
Argument type - array type <-----------<<<
Result type - INTEGER
Function - equivalent to LEN(v, 0)
Argument type - String
Result type - INTEGER
Function - length of string (not counting 0X)
So I now agree with you - it does appear that the change was intentional.
Chris Burrows
CFB Software
http://www.cfbsoftware.com
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Received on Mon Dec 13 2004 - 11:27:49 UTC