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From: rbowman <bowman@montana.com>
Newsgroups: alt.folklore.computers,comp.os.linux.misc
Subject: Re: The joy of FORTRAN
Date: 19 Oct 2024 03:03:55 GMT
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On Fri, 18 Oct 2024 05:41:41 -0000 (UTC), Lawrence D'Oliveiro wrote:

> On 18 Oct 2024 04:35:09 GMT, rbowman wrote:
> 
>> Our source tree still has vestiges of Fortran that go back more than 20
>> years and are strictly f77.
>> 
>> 	  recnum = 1 read(adrich,15,rec=recnum) totrec
>> 15	  format(i10)
>> 
>> 100	 if(recnum.gt.totrec) goto 500
>> 	  read(adrich,105,rec=recnum+1) ch
>> 105	 format(1a1)
> 
> You know that Fortran 77 introduced if-then and do-while, right?

In fact the continuation of the snippet is

105	 format(1a1)
	  if(ch.ge.'A' .and. ch.le.'Z') then
	    index = ichar(ch) - 64
	  else if(ch.ge.'1' .and. ch.le.'9') then
	    index = ichar(ch) - 22
	  else
	    index = 36
	  endif

All the DO constructs are variations on

	DO 11 k=1,strlen
	  STNAME(k) = ' '
11	CONTINUE

I'm not about to argue the niceties of ANSI Fortran 77 but

https://web.stanford.edu/class/me200c/tutorial_77/09_loops.html

while-loops
The most intuitive way to write a while-loop is

      while (logical expr) do
         statements
      enddo
or alternatively,

      do while (logical expr) 
         statements
      enddo
The program will alternate testing the condition and executing the 
statements in the body as long as the condition in the while statement is 
true. Even though this syntax is accepted by many compilers, it is not 
ANSI Fortran 77. The correct way is to use if and goto:

label if (logical expr) then
         statements
         goto label
      endif