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Douglas G. Danforth a écrit :
>
>
> Gérard Meunier wrote:
>> Douglas G. Danforth a écrit :
>>> Folks,
>>> I just discovered that the length of a string varies depending
>>> upon whether it is used directly or passed as an argument to
>>> a procedure for example
>>>
>>> VAR x: ARRAY 32 OF CHAR;
>>> x := "HI";
>>>
>>> will have length
>>> LEN(x$) = 2
>>> but will have length
>>> LEN(y) = 3
>>> when it is passed to a procedure with argument y.
> ...
>> It's because you pass x$, and not x itself. x$ is the string inside
>> the array of char, so its length is the length of the string plus 1
>> (terminal 0X).
>>
>> Gérard
> Ah, but if x$ is a "string" which you seem to imply includes the
> terminal 0X then when I call
> LEN(x$) in the outer procedure I should also get the value 3 and not
> 2. There seems to be
> an inconsistency.
Here is how I see what happens: when x is passed to an IN parameter, its
address is copied, so formal and actual parameters are identical; when
x$ is passed, a new array of char is created, whose length is just
enough to contain x$ (LEN(x$) + 1), x$ is copied into it and the new
array is passed as actual parameter. In the last case, LEN(y$) = LEN(x$)
and LEN(y) = LEN(x$) + 1.
Gérard
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Received on Fri Sep 29 2006 - 20:23:47 UTC