bugModula-2 Compiler and Translator - Bugs: bug #44789, Enhancement: cast, shift and rotate


bug #44789: Enhancement: cast, shift and rotate

Submitter:  None
Submitted:  Thu 09 Apr 2015 07:19:38 AM UTC
Category:  None Severity:  1 - Wish
Item Group:  None Status:  Confirmed
Privacy:  Public Assigned to:  None
Open/Closed:  Open
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Thu 23 Apr 2015 03:42:43 PM UTC, comment #1: 

I'm happy to receive your patches. :)

David Egan Evans <sinuhe>
Project Administrator
Thu 09 Apr 2015 07:19:38 AM UTC, original submission:  

Contrary to popular believe, Wirth did not "invent" Modula-2. Instead, he took Xerox' Mesa language as it was and recast it in Pascal syntax to derive Modula-2. The only innovation he applied was the introduction of the SYSTEM module for unsafe language features. Unfortunately, Wirth did not consequently apply his own philosophy, several unsafe features remained in the language without requiring import from SYSTEM.

One such unsafe feature is the unsafe type transfer, aka cast operation. The ISO Modula-2 standard -- for all its failings -- corrected this particular shortcoming by replacing Wirth's innocent looking cast syntax with an explicit CAST function macro that had to be imported from module SYSTEM.

Wirth's PIM language report does allow for additions to module SYSTEM. Consequently, adding ISO's CAST function macro to a PIM Modula-2 compiler does not technically render the compiler non-compliant with the PIM standard.

Also, m2c already added ISO function VAL (safe type transfer) as a language extension. This should have gone hand in hand with adding CAST to module SYSTEM.

Also, for any serious low-level work, shift and rotate operations are required. Those should also be added to module SYSTEM. Again, this is entirely compliant with Wirth's PIM language description since it allows for unsafe language features to be added to module SYSTEM at the discretion of the implementor.



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    Follow 2 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2015-04-23 sinuhe Severity3 - Normal 1 - Wish
        StatusNone Confirmed

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