Path: utzoo!mnetor!uunet!tektronix!reed!douglas
From: douglas@reed.UUCP (P Douglas Reeder)
Newsgroups: comp.lang.pascal
Subject: Re: Scope question
Message-ID: <8601@reed.UUCP>
Date: 31 Mar 88 20:21:44 GMT
References: <718@virginia.acc.virginia.edu>
Reply-To: douglas@reed.UUCP (P Douglas Reeder)
Organization: Reed College, Portland OR
Lines: 49

In article <718@virginia.acc.virginia.edu> scl@virginia.acc.virginia.edu (Steve Losen) writes:
>The following pascal program compiles and outputs "10" with the Berkeley
>pascal compiler "pc".
>
>program test(output);
>	const c = 10;
>
>procedure junk;
>	const c = c;  { Shouldn't this be an error ? }
>[rest of program deleted]
>
>As far as I can tell, then, the pascal fragment
>
>const c = c;
>
>should not be allowed even if c is a constant defined in an enclosing
>block.  Is my interpretation of the pascal standard correct?  Since I'm
>writing a pascal compiler, I need to have this issue cleared up.
>
>-- 
>Steve Losen     scl@virginia.edu
>University of Virginia Academic Computing Center

In the line 
        const c = c;
the reference to c on the right refers to the previously defined constant c
and the reference on the left refers to the newly defined constant c. 
In procedure junk, before this statement (that is, in previous constant 
declarations), c refererred to the first c.  After, c refers to the local c.
In some sense, the right side of the statement is compiled before the left 
hand side.  The following code does exactly the same thing, using slightly 
different names:

program test(output);
	const c1 = 10;

procedure junk;
	const c2 = c1;
[rest of program ]

The same thing happens with your second example [not shown].
My book does not make clear if this is ISO standard.  Either way, its 
meaning is unambiguous.

-- 
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