| Re: Another small V8.0 bug [message #71891 is a reply to message #71889] |
Mon, 26 July 2010 10:59   |
penteado
Messages: 866
Registered: February 2018
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On Jul 26, 2:12 pm, wlandsman <wlands...@gmail.com> wrote:
> I have found another bug in V8.0, at least for users who still have
> round parenthesis used for indices lurking around in their code.
> Like Mike Potter's example, it is not easily repeatable, and for
> example sometimes only occurs after compile the program a second
> time. And because it occurs in a fairly large program, I have not
> yet isolated it into a simple test program. But I can illustrate
> the problem after placing a STOP statement
>
> % Stop encountered: SHOWDB 72 /home/landsman/uvot/bpm16274/
> showdb.pro
> IDL> help,list
> LIST LONG = Array[1]
> IDL> print,list[0]
> 183
> IDL> print,list(0)
> 0
> IDL> help,list(0)
> <Expression> LIST <ID=22 NELEMENTS=1>
> IDL> print,list(0) LE 0
> % Unable to convert variable to type object reference.
> % Execution halted at: SHOWDB 72 /home/landsman/uvot/
> bpm16274/showdb.pro
> % $MAIN$
>
> IDL> print,!version
> { x86 linux unix linux 8.0 Jun 18 2010 32 64}
Do you mean that this does not happen every time? To me this seems to
be the expected behavior. The line
print,list(0)
Is creating a list (which is an object), containing one element, and
printing it. The same with the use of help.
>
> So IDL seems confused as to whether 'list' is a variable or an
> object. (The code is all imperative statements with no object
> syntax). Note that this differs from the long-standing variable/
> function ambiguity that can occur when using the () syntax for
> indexing. --Wayne
Actually, this is the same old function/variable ambiguity. In this
case, between the array called list, and the function called list() -
which just happens to be the function that creates a list object. The
only new things here is that objects can be instantiated with the
syntax object=class(), which is equivalent to
object=object_new('class'), and that since there is a new builtin
class called 'list', that line is being interpreted as a function
call.
Perhaps the variability you report is from the context, which
determines whether () are interpreted as indexing or function call,
since that depends on which variables are currently defined, and which
functions are currently compiled.
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