3 Feb
2022
3 Feb
'22
5 a.m.
On 1/31/22 2:46 PM, Will Senn wrote:
All,
I have been doing some language exploration in v7/4.3bsd and came
across Software Tools (not the pascal version). It's written using
ratfor, which I had seen in the v7 UPM. I fired up v7 and tried my
hand at the first example:
I thought I'd close the loop on the language side of this thread. I am
happy to report that ratfor (and fortran) is alive and well. It works on
my mac! The Software Tools book is awesome, if challenging. The first
chapter is particularly challenging as it takes a bit to figure out
where the authors are coming from and what they include, exclude, and
highlight... and why. The key to understanding the book, as a modern
reader, is to understand that the authors assume their readers are
fortran (or PL/I) programmers. Because of this, they don't explain
anything that would be obvious to said programmers (read, write, LUNs,
Hollerith cards, format, etc). In addition, they will push down details
of implementation until they practically disappear (think singularity...
annoyingly consistent in this regard). When they say something like "EOF
is a symbolic constant... We won't tell you what its value is, since the
particular value doesn't matter", they really mean it. Unfortunately, in
order to actually implement stuff, you gotta know what every symbolic
constant and macro replacement is :).
For example, even in the tiny copy program example, from the
introductory chapter, once you include the primitive getc and putc
subroutines, there are 7 symbolic constants: MAXLINE, MAXCARD, NEWLINE,
STDIN, STDOUT, EOF, SPACE and character, which is really an integer and
gets replaced with integer by some mythical preprocessor (chapter 8).
Anyhow, in the modern world, MAXLINE and MAXCARD don't really have
meaning, but they can magically be treated as lines of a file, the rest
do have meaning, but they don't evaluate to the same things in
Fortran-land as in modern-land. STDIN is 5 and STDOUT is 6 (card reader
and punch LUNs, again some magic that lets them be treated as terminal
input and output), EOF is -1, SPACE is 32, NEWLINE is 10. Anyhow, long
story just a bit shorter, replace those constants, swap character for
integer, and combine getc, putc, and copy and yahoo, a working copy
program that works in v7, 4.xBSD, and Mac OS X Mojave (and BSD, etc),
without any further modifications... at all.
Included for the curioius (copynew.r):
# on v7
# $ ratfor -C copynew.r > copynew.f
# $ f77 -o copynew copynew.f
# on mac
# $ ratfor77 -C copynew.r > copynew.f
# $ gfortran -o copynew copynew.f
# $ ./copynew
# This is a test.
# This is a test.
# CTRL-d
# $
# getc (simple version) - get characters from standard input
integer function getc(c)
integer buf(81), c
integer i, lastc
data lastc /81/,buf(81) /10/
lastc = lastc + 1
if(lastc > 81) {
read(5, 100, end=10) (buf(i), i = 1, 80)
100 format(80 a 1)
lastc = 1
}
c = buf(lastc)
getc = c
return
10 c = -1
getc = -1
return
end
# putc (simple version) - put characters on the standard output
subroutine putc(c)
integer buf(80), c
integer i, lastc
data lastc /0/
if (lastc > 80 | c == 10) {
for (i = lastc + 1; i <= 80; i = i + 1)
buf(i) = 32
write(6, 100) (buf(i), i = 1, 80)
100 format(80 a 1)
lastc = 0
}
if (c != 10) {
lastc = lastc + 1
buf(lastc) = c
}
return
end
# copy - copy input characters to output
integer getc
integer c
while(getc(c) != -1)
call putc(c)
stop
end
Of course, it's criminal to have all those hardcoded magic numbers,
wouldn't it be swell if there were some sort of macro facility?... oh,
wait, that's what Chapter 8's all about... I can't wait.
Will