[TUHS] ratfor vibe

Will Senn will.senn at gmail.com
Thu Feb 3 14:00:21 AEST 2022

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

    10      c = -1
             getc = -1

    # 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

    # copy - copy input characters to output
             integer getc
             integer c

             while(getc(c) != -1)
                     call putc(c)

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.

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