Eiffel suggestion

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3 total messages Started by jwg1@bunny.UUCP Wed, 21 Dec 1988 23:29

#20

Author: jwg1@bunny.UUCP
Date: Wed, 21 Dec 1988 23:29

39 lines
1154 bytes

One of the things that drove me nuts about Simula 67 was the absence
of a concatenation operator. It did have a TEXT attribute called
CONCAT, but it was rather unwieldy to use if you had to do much string
processing at all.

Unfortunately, unless I missed something, Eiffel doesn't even have a
CONCAT feature for STRING.  It does have prepend and append, but they
change the string they are applied to.  It would be nice to also have
something like this as a feature of STRING:

cat (s: STRING): STRING is
		-- Concatenate a copy of s to current string and return it
	local
		newstring: STRING;
	do
		newstring.Create( current.length + s.length );
		newstring := Current.duplicate;
		newstring.append( s );
		Result := newstring.duplicate
	end; -- cat

Thus,
	x: STRING is "Foo";
	putstring( x.cat("f").cat("a").cat("h!") );
yields:
	"Foofah!"
without changing x.

Try to do that with append !

Of course, "a".cat( x ) is NOT valid.  Maybe this makes sense from some
point of view, but certainly not from one of convenient language features.

Cheers.
--
Jim Gish
GTE Laboratories, Inc., Waltham, MA
CSNET: jgish@gte.com    UUCP:  ..!harvard!bunny!jwg1

Re: Eiffel suggestion

#23

Author: jwg1@bunny.UUCP
Date: Thu, 22 Dec 1988 15:49

34 lines
1691 bytes

In article <6385@bunny.UUCP> jwg1@bunny.UUCP (that's me) wrote:
>One of the things that drove me nuts about Simula 67 was the absence
>of a concatenation operator. It did have a TEXT attribute called
>CONCAT, but it was rather unwieldy to use if you had to do much string
>processing at all.

I realized after I posted this, that Simula did NOT have a CONCAT TEXT
attribute.  In fact, it was less well equipted than Eiffel since it
didn't have an append or prepend.  It's been so long since I've been
fortunate enough to use Simula, that I forgot that I had my own concat
function.  My apologies to other Simula aficianados for the incorrect info.

In all fairness to Eiffel, so far I think it looks like a very good
language.  And it good be a great language if minimal steps are taken
to add certain language features.  For example, a Loop construct with
an exit and a Case statement are really needed.  The decision to have
only an "until" clause, and not provide a "while" clause is a mistake.
Some loop conditions read much better as "while" clauses, and if they
read better, there probably is a better chance of them being written
correctly.

Although the designers goal of keeping the language simple is a noble
one, without certain powerful yet elegant capabilities, like
loop/exit, it becomes tedius to write large programs.  I realize that
the preference for certain language features is subjective, but I
think Eiffel needs some "shaking out" to determine what needs to be
added.  I hope that the members of this newsgroup can make a positive
contribution to doing just that.

--
Jim Gish
GTE Laboratories, Inc., Waltham, MA
CSNET: jgish@gte.com    UUCP:  ..!harvard!bunny!jwg1

Re: Eiffel suggestion

#26

Author: newsuser@LTH.Se
Date: Wed, 28 Dec 1988 13:28

26 lines
1002 bytes

>One of the things that drove me nuts about Simula 67 was the absence
>of a concatenation operator.
>...
>Unfortunately, unless I missed something, Eiffel doesn't even have a
>CONCAT feature for STRING.  It does have prepend and append, but they
>change the string they are applied to.

The current standard of Simula DOES have a text concatenation operation. This
operator always creates a new text object and does not change any of the
operands. Both constants and variables can be handled by the operator.
Example:
   begin
      text x = "Foo";   ! --- Declaration of text constant ---;
      sysout.outtext(x & "f" & "a" & "h!");
   end;
This program yields "Foofah!" on the standard output.

The current standard of Simula is published as a Swedish national standard
document: SS 636114 (ISBN 91-7162-234-9). It is available via all other national
standardization bodies. (And via Simula vendors.)
---
Gorel Hedin
Dept. of Computer Science.
Lund Institute of Technology, Sweden
gorel@dna.lth.se

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