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Path: utzoo!linus!decvax!harpo!floyd!clyde!ihnp4!inuxc!pur-ee!iuvax!cjl
From: cjl@iuvax.UUCP
Newsgroups: net.lang
Subject: Re: Anti-CLU... Anti-Strong-Typing... - (nf)
Message-ID: <1201@pur-ee.UUCP>
Date: Sat, 3-Dec-83 18:26:01 EST
Article-I.D.: pur-ee.1201
Posted: Sat Dec  3 18:26:01 1983
Date-Received: Sun, 4-Dec-83 09:28:17 EST
Sender: notes@pur-ee.UUCP
Organization: Electrical Engineering Department , Purdue University
Lines: 71

#R:dartvax:-41100:iuvax:11800004:000:3133
iuvax!cjl    Dec  3 17:20:00 1983


     From Abstract data type point of view, the data having  the  same
structure  don't  have  to have the same type names. That sounds quite
reasonable. But from software engineering point  of  view,  we  cannot
ignore  efficient  implementation.   In  Modula-2, Wirth offers a good
solution.  The  language  itself  allows  non-strong-type  programming
(called  low  level  programming)  with  strong warning to the user by
enforcing them to be imported from MODULE SYSTEM.

     While Pascal may appear  too  restrictive  and  C  irresponsible,
Modula-2 do resolve these conflicts quite beautifully.  The low  level 
features in Modula-2 include :
(1)  a low level type WORD and a complete set of type  transfer  func-
     tions whenever the operands have the same storage.
(2)  a low level type ADDRESS as the first class citizen  with  refer-
     ence  function  ADR and dereference function ^ and all operations
     derived from the CARDINAL type.
(3)  a typeless dynamic  storage  allocation  procedure  ALLOCATE  and
     storage size functions SIZE(var) and TSIZE(type).
(4)  a Sequence type called "open array" which follows the rule  of
     structure compatibility. As a low level feature, the open array is
     more consistent then Ada's unconstraint arrays.  Remember even we
     have the same "sequence" structure, we may still want to give them 
     different type names !

     Again these are low level features  which  should  be  used  with
extreme care.  So I think Modula-2 has resolved the problem now and we
can put C and Bliss to rest now.

From Chingmin Jim Lo
     Dept. of Computer and Information Science
     Indiana University-Purdue university at Indianapolis
     CSNET : cjl@Indiana@Rand-relay

From Abstract data type point of view, the data having the
same structure don't have to have the same type name.
That sounds quite reasonable. But from software engineering
point of view, we cannot ignore efficient implementation.
In Modula-2, Wirth offers a good solution. The language itself
allows non-strong-type programming (called low level programming)
with strong warning to the user by enforcing them to be imported
from MODULE SYSTEM. 
.pp
While Pascal may appear too restrictive and C irresponsible, 
Modula-2 DO resolves these conflicts in a quite beautiful way.
The low level features include :
.np
a low level type WORD and a complete set of type transfer
functions whenever the operands have the same storage.
.np
a low level type ADDRESS as the first class citizen with
reference function ADR and dereference function ^  and
all operation of the CARDINAL type.
.np
a typeless dynamic storage allocation procedure ALLOCATE
and storage size functions SIZE(var) and TSIZE(type).
.np
a Sequence type called "ARRAY OF type" which follows the rule
of struture compatibility. As a low level feature, the open
array is more consistent then Ada's unconstraint arrays.
Remember even we have the same structure "sequence", we may
want to give them different type names !
.pp  
Again these are low level features which should be used with
extreme care. So why do we need C except for UNIX ?