🚀 go-pugleaf

Andreas Borchert (borchert@titania.mathematik.uni-ulm.de) wrote
in reply to Markku Sakkinen <sakkinen@jyu.fi>:
: Agreed, programmers shouldn't be enforced to use VAR-parameters
: for reasons of efficiency only. But, even with the semantics of
: Oberon or Modula-2, it's not to difficult for the compiler to
: detect that your 1000 x 1000 array isn't modified and, thus,
: doesn't need to be copied.

That doesn't work as soon as your procedure is public and (directly or
indirectly) calls some procedure not fully known to the compiler, since
the original argument may be accessible and modified behind the back of the
supposedly innocent routine. According to the current definition it only
sees a copy made at the entry and therefore would not be influenced by the
perfectly legal modification, but due to our smart optimizer ... :-(

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