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prehistory of m4

From: Doug McIlroy
Subject: prehistory of m4
Date: Wed, 30 May 2012 00:50:05 -0400
User-agent: Heirloom mailx 12.5 7/5/10

The series of GPM-like macroprocessors at Bell Labs stretches
back further in time than is described in the History section
of the texinfo manual for m4.   Macros were quite a cottage
industry there.

The names m3 and m4 were prefigured by m6, written by Andrew
D. Hall as a tool to parameterize the Fortran source for the 
Altran computer algebra system to facilitate porting among multiple
platforms.  The manual for m6 is at
http://cm.bell-labs.com/cm/cs/cstr/2.pdf. Kernighan and Plauger
were inspired by that model.

Hall's m6 in turn was based on models that Robert Morris
and I described in an unpublished memorandum in 1970. The
code for one of those models was originally written by me
in 1968 during a visiting lectureship in Strachey's lab,
so the connection to GPM is quite intimate.  My Snobol fit on a
page, but of course used the whole Snobol interpreter, while
GPM fit in 250 machine instructions.  Strachey was a brilliant

The three predecessors mentioned above were, in chronological
order, written in Snobol 3, Fortran, and Ratfor, so their
source code looked far less similar than their behaviors.

Doug McIlroy

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