Write Fortran in Ruby

Ruby
1

A fun, but ultimately pointless exercise from the “Python
for Fortran Programmers” thread in news:comp.lang.fortran:

Try to write the following Fortran 77 program (note the
6 space indentation) in Ruby so that it looks as close
to the Fortran as possible without extending Ruby:

   program ii
   integer i
   do i=0,10
      print*,i
      if (i.gt.5) goto 1
   enddo

1 print*,i*i
end

Here’s the Python candidate to date:

for i in range(10):
#begin
print i
if i>5: break
#end
print i*i

May an alternative solution which extends Ruby with
a mini Fortran DSL would also be interesting?

2

Bil K. wrote:

1 print*,i*i
end

My Fortran’s a little rusty (I never learnt it); does this program do
the
right thing?

 #program ii
 #integer i
  for i in 0..10
     print *i
     if (i.>5) then break end
  end#do

1; print ii
#end

Cheers,
Dave

3

Bil K. wrote:

1 print*,i*i
end

Sorry, output should be:

0
1
2
3
4
5
6
36

4

I said earlier:

#program ii
#integer i
 for i in 0..10
    print *i
    if (i.>5) then break end
 end#do

1; print ii
#end

A bad guess. Swap the prints for putses like this:
puts *i
…
1; puts ii

Any ideas for making “then break end” look more like “goto 1”?

Cheers,
Dave

5

Your Fortran program is not legal since the value of i outside the loop
is not defined. Over the years, I have seen are 6, 7 and runtime error
(although you are not likely to see the latter with slack modern
workstation compilers) as a value.

I would suggest putting the print of i*i inside a block if.

6

On Fri, 3 Mar 2006, Dave B. wrote:

A bad guess. Swap the prints for putses like this:
puts *i
…
1; puts ii

Any ideas for making “then break end” look more like “goto 1”?

Cheers,
Dave

 harp:~ > cat a.f
       program ii
       integer i
       do i=0,10
          print*,i
          if (i.gt.5) goto 1
       enddo
 1     print*,i*i
       end



 harp:~ > f77 a.f && a.out
  0
  1
  2
  3
  4
  5
  6
  36


 harp:~ > cat a.rb

 i = catch('1') do
   (0..10).each do |i|
     puts i
     throw '1', i if i > 5
   end
 end
 puts i * i


 harp:~ > ruby a.rb
 0
 1
 2
 3
 4
 5
 6
 36

-a

7

In an attempt to make it look at close to the fortran and still run
(even if silly):

   :program; i = 0
   Integer i
   i.upto(10) do |i|
   print i,$/
       if (i > 5) : break end
   end
   print i*i,$/
   exit
8

I guess using a range is slightly better. I know, enough already. I
just wanted it to match the same number of lines (8) and look as close
as I could.

   :program; i = 0
   Integer i
   (0..10).each do |i|
       print i,$/
       if (i > 5) : break end
   end
   print i*i,$/
   exit
9

Hi!

At Thu, 2 Mar 2006 20:48:37 +0900,Bil K. wrote:

   enddo

1 print*,i*i
end

First of all there is no programming language calles “Fortran 77”. The
correct name is “FORTRAN 77”. The spelling “Fortran” is used for more
recent versions like “Fortran 90”. Next the above program is no valid
FORTRAN 77. If a compiler sticks to the FORTRAN 77 specification it
will issue a syntax error because “enddo” is unknown to it. FORTRAN 77
do-loops start with the DO keyword followed by a label. The label
names the line that marks the end of the loop. The labelled statement
must be an executable one. People tend to use “continue” for this
purpose.

   program ii
   integer i
   do 1 i=0,10
      print*,i
      if (i.gt.5) goto 2

1 continue
2 print*,i*i
end

If your compiler supports “end do” (which is no F77) it may as well
support “exit” (which isn’t either) so that you can write:

   program ii
   integer i
   do i=0,10
      print*,i
      if (i.gt.5) exit
   end do
   print*,i*i
   end

Besides that all variables starting with an ‘i’ are already integers
so that you can write

   program ii
   do i=0,10
      print*,i
      if (i.gt.5) exit
   end do
   print*,i*i
   end

Nevertheless I prefer Fortran 90+ and write

program ii
do i=0,10
print*,i
if (i>5) exit
end do
print*,i*i
end

You may need to provide the command line option “-free” or similar :->

I learned FORTRAN 77 on an IBM Mainframe using a terminal that had a
“Mixed case display/Uppercase only display” switch :slight_smile:

Josef ‘Jupp’ Schugt