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From: cik@l.cc.purdue.edu (Herman Rubin)
Newsgroups: comp.theory
Subject: Re: Why not multiple out parameters? [again]
Summary: Gross inefficiency is the result
Message-ID: <2501@l.cc.purdue.edu>
Date: 1 Sep 90 15:22:46 GMT
References: <1990Aug28.203643.11214@zaphod.mps.ohio-state.edu> <4019@rex.cs.tulane.edu>
Organization: Purdue University Statistics Department
Lines: 37

In article <4019@rex.cs.tulane.edu>, fs@rex.cs.tulane.edu (Frank Silbermann) writes:
> 
> In article <11831@ogicse.ogi.edu>
> dinucci@ogicse.ogi.edu (David C. DiNucci) writes:
| >
| >	... at higher "system" levels
| >	modules are being composed which each do a fair amount of work,
| >	and thus are likely to return many different kinds of results.
| >	Plugging these results into a record structure
| >	just so they can be pulled back apart again is nonproductive.
> 
> When a collection of diverse of values
> forms a single conceptual unit,
> it should be treated as a unit within the program.
> Therefore we define a record-type to represent the concept,
> 
> If a module's different kinds of results
> do _not_ form a conceptual unit,
> then the design is kludgy and should be redone.
> What ever happened to the idea that every module
> should perform a single conceptual operation
> (i.e. produce a single conceptual result)?

Kludgy it is not.  For example, a procedure can produce a result and a
domain indicator, such as the truth of a condition.  Or an integer
quotient and a floating remainder can be produced.  Or a short integer
exponent and a mantissa.  Or the decomposition of a word into fields,
one being translated into a sign, another into an integer, and the 
rest into a floating point number. 

All of these are natural and useful multiple outputs.  Putting these 
into a record to extract later is very definitely non-productive, just
as encoding multiplication as repeated addition is non-productive.
-- 
Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907
Phone: (317)494-6054
hrubin@l.cc.purdue.edu (Internet, bitnet)	{purdue,pur-ee}!l.cc!cik(UUCP)