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Re: Wondering about compile time error checking
From: |
Charles Staelin |
Subject: |
Re: Wondering about compile time error checking |
Date: |
Tue, 20 Jun 2000 20:34:04 -0400 |
Yes, Java handles this in the same way. There would be no error until run time.
Charles
>>> address@hidden 06/20/00 17:58 PM >>>
Paul Johnson wrote:
> I'm running the swarm snapshot June 6, 2000.
>
> I wrote a dynamic scheduling setup and mistakenly got a selector wrong.
> A statement:
>
> [schedule at: x createActionTo: self message: M(moveTo:): position ];
>
> Referred to a nonexistent method, moveTo:, so the program crashed with
> no message like "object does not respond to "moveTo:". Could there be
> or has there ever been compile-time checking to see if objects implement
> the method in the createActionTo: statement? I keep thinking there used
> to be a warning about this kind of mistake.
The compiler is not required to check which method in which class moveTo:
refers. The instance of the Schedule class is
being passed a method selector for moveTo: and stores it in a variable, and a
pointer to an object which 'self' referred
to. At compile time all that is required of the compiler is that it checks that
the schedule exists and responds to
createActionTo:message:. The runtime error is a cost of doing business in this
fashion.
I believe that the Java implementation would also allow this error to go
unnoticed until at runtime. Correct me if I'm
wrong.
--Benedikt
--
Bushism of the day
--------------------------------------------------
GOV. BUSH: Because the picture on the
newspaper. It just seems so un-American to me,
the picture of the guy storming the house with
a scared little boy there. I talked to my
little brother, Jeb--I haven't told this to
many people. But he's the governor of--I
shouldn't call him my little brother--my
brother, Jeb, the great governor of Texas.
JIMLEHRER: Florida. GOV. BUSH: Florida. The
state of the Florida.
George W. Bush, Governor of Texas
--The NewsHour With Jim Lehrer, April 27, 2000
(Source: Jacob Weisberg in Slate magazine)
--------------------------------------------------
--
Benedikt Stefansson | address@hidden
CASA, Inc. | Ph : (505) 988-8807 x101
Santa Fe, NM 87501 | Fax: (505) 988-3440
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Swarm-Support is for discussion of the technical details of the day
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with "help" in the body of the message.