Re: The semantics of the for-loop

Article View: comp.lang.modula2

Article #4207

#4207

From: Robert Firth
Date: Mon, 18 Apr 1988 14:28

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In article <2455@pasteur.Berkeley.Edu> seitz@cory.Berkeley.EDU.UUCP (Matthew Eric Seitz) writes:

]_Programming_In_Modula-2_ essentially defines the for statement as the following
]equivalency
]
]"FOR" ident ":=" expression1 "TO" expression2 [ "BY" ConstExpression ] "DO" 
]	StatementSequence
]"END"
]is equivalent to
]
]ident ":=" expression1;
]"WHILE" ident "<=" expression2 "DO"
]	StatementSequence
]	[ident ":=" ident "+" ConstExpression (* if "BY" clause used *) |
]	 ident ":=" ident "+ 1" (* if "BY" clause not used *) ]";"
]"END"
](* ident := undefined *)

It does.  And thereby perpetuates the design or implementation error that
has cursed FOR-loops since the days of Algol-60: a loop set to end on the
largest value of the associated type will fail.

This is 1988.  Let's at least put THAT right!

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Path: arc1-ca.pugleaf.net!utzoo!mnetor!uunet!husc6!mailrus!rutgers!rochester!pt.cs.cmu.edu!sei!sei.cmu.edu!firth
From: firth@sei.cmu.edu (Robert Firth)
Newsgroups: comp.lang.modula2
Subject: Re: The semantics of the for-loop
Message-ID: <5099@aw.sei.cmu.edu>
Date: 18 Apr 88 14:28:18 GMT
References: <5571@uwmcsd1.UUCP> <2455@pasteur.Berkeley.Edu>
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