Conference turris::languages

26.0. "LITERATE PROGRAMMING" by SYZYGY::SOPKA () Tue Sep 04 1984 03:37

	In a recent issue of THE COMPUTER JOURNAL (Vol 27 #2), Donald Knuth
has published a paper titled "Literate Programming".  In it he says:

	"Let us change our traditional attitude to the construction
    of programs: Instead of imagining that our main task is to instruct
    a 'computer' what to do, let us concentrate rather on explaining
    to 'human beings' what we want a computer to do.

	"The practitioner of literate programming can be regarded as
    an essayist, whose main concern is with exposition and excellence
    of style.  Such an author, with thesaurus in hand, chooses the
    names of variables carefully and explains what each variable means.
    He or she strives for a program that is comprehensible because its
    concepts have been introduced in an order that is best for human
    understanding, using a mixture of formal and informal methods
    that nicely reinforce each other."

	He goes on to describe a programming language system which he 
calls WEB.  "WEB itself is chiefly a combination of two other languages:
(1) a document formatting language and (2) a programming language. 
. . . A WEB user writes a program that serves as the source language for
two different system routines.  One line of processing is called 'weaving'
the web; it produces a document that describes the program clearly and
that facilitates program maintenance.  The other line of processing is
called 'tangling' the web; it produces a machine executable program. The
program and its documentation are both generated from the same source,
so they are consistent with other."

	The prototype system he has developed and which he uses in this 
paper to describe his concept of Literate Programming is based on TEX 
as the document formatting language and on PASCAL as the programming 
language.  He does claim, however, that "the same principles would apply
equally well if other languages were substituted."  To support this
claim he references a report on the development of "CWEB, based on
Troff/Nroff and C instead of TEX and PASCAL."

	Beyond discussion of the philosophy and design of WEB, the 
paper includes:
    1.) the details of a WEB program to compute prime numbers;
    2.) the applicability of Occam's Razor to WEB;
    3.) discussion of issues involved in the portability of WEB;

	Finally, he concludes: 

	"I made a concious decision not to design a language that 
    would be suitable for everybody.  My goal was to provide a tool
    for systems programmers. . .[but it] may be only for the subset
    of computer scientists who like to write and to explain what
    they are doing.  My hope is that the ability to make explan-
    ations more natural will cause more programmers to discover
    the joys of literate programming."

	This seems to emphasize an axis of concern which is orthogonal
to those usually discussed in the design of programming languages.
Pick up a copy at your local technical library and decide for yourself
whether this is bound to become an important reference work in programming
language design or is just another unrealistic, academic's pipe dream.