Re: [BLACKBOX] Matrix slices - syntax

From: [at]} <Alexander>
Date: Fri, 2 Apr 2010 10:57:22 +0800

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Hello!

DGD> I also wonder why VectorA does not match VectorB.
DGD> I can understand it is easier for a compiler to just check
DGD> the identifier rather than the semantics underlying it BUT
DGD> the internal representations are identical.

DGD> So if John calls it a pig and Tom calls it a swine then
DGD> "it" is not the same in the two cases?

  Consider independent compilation.

  Say, in module A you have:
  TYPE
     Vector* = ARRAY 3 OF REAL;
  PROCEDURE Proc* (VAR v: Vector);...

  And in module B you have:
  IMPORT A;
  PROCEDURE SomeProc;
  VAR v: ARRAY 3 OF REAL;
  BEGIN
     A.Proc (av);
  END SomeProc;

  The call A.Proc from B in illegal in Oberon, but what if it was
  legal, based on the assertion that the A.Vector and the anonymous
  type in B.Proc are "the same"? Let's say that we have the module B
  precompiled, and then we change the definition of A.Vector to be
  ARRAY 13 OF REAL. Technically, only the A.Vector type was udpated,
  which is not imported in B. B only uses A.Proc, and its interface
  was not modified, so there is no reason to recompile B.

  So, now we have the precompiled module B, which loads successfully
  passing the compatibility checks, but which supplies incorrect
  parameter to the A.Proc.

---=====---
 Alexander

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Received on Fri Apr 02 2010 - 04:57:22 UTC