break, et cetera

[Chris Torek]

For those who wish to read the `original' article (I have not),
here is the reference:

Knuth, D. E., `Structured Programming with GOTO Statements',
_Computing_Surveys_, 6, 4, 1974, 261-301.

The idea is to use `goto' in a very restricted way to express what
the code is supposed to *do*: For example, if you are searching
for something, and need to do `x' if it is not found, but `y' if
it is, then doing a `goto found' and separating the code for `y'
from the code for the search is quite reasonable. Others, of
course, will argue that the code for `x' and `y' should be moved
to other routines; but I believe this kind of separation can be
overused, just as can `goto's.

[The information in the next few paragraphs prompted me to add
net.lang.pascal to the Newsgroups line above. Please stop here
if bored.]

Knuth's usage of `goto' and even `return' may be found in the source
to TeX and MetaFont, which are written in WEB, a language combining
a Pascal preprocessor and a program description/documentation
language. The `Tangle' processor converts a WEB file to a Pascal
file; and the `Weave' processor converts a WEB to a TeX file.
(Incidentally, there is an interesting bootstrap problem here, as
both Tangle and Weave are also written in WEB.)

This may again be more a personal preference than anything else,
but I find that Knuth's programs written in WEB are considerably
easier to read than many other smaller programs I have seen written
directly in Pascal. Even the `return' statements---which are
actually `goto's in disguise, and rather thin disguise at that---are
better than the convoluted code with extra booleans found in programs
that steadfastedly avoid the `goto temptation'.

The WEB system is available for 4.1 and 4.2 BSD Unix as part of
the Unix TeX distribution. (There is a distribution fee, around
$75, I think.) Contact Pierre MacKay at the University of Washington
for more information: ARPA: MacKay@WASHINGTON; UUCP:
...!uw-beaver!mackay.
--
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 4251)
UUCP: seismo!umcp-cs!chris
CSNet: chris@umcp-cs ARPA: ch...@mimsy.umd.edu