Digit Separator

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1

Does Fortran have a digit separator for integers? Seems like a good feature to have if it is not already there.
https://en.cppreference.com/w/cpp/language/integer_literal

2

Not as far as I know.
But lol, you could use F77 fixed format, where space is insignificant:

c This is a fixed form file (.f)
      program test
      i = 1 000 000
      print *, i
      end program
3

One can also use spaces as digits separator in input data, with explicit format and blanks interpretation set to ‘null’ (default) or forced by bn control descriptor

program blanks
  read(*,'(bn,i20)') i      !   1 234 567
  print *, i                !     1234567
end program blanks
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4

@fortran4r , if your questions pertains to integer literals, as in say what the Fortran standard terms int-literal-constant, the conforming digit-string per the current standard allows no spaces or any other separators.

The BNF form being: digit[digit]...

5

I like they way Rust achieves this:

// Use underscores to improve readability!
println!("One million is written as {}", 1_000_000u32);

A Fortran compiler would try to interpret this as a 1 of the type 000_000u32 which obviously cannot exist.

But I think this could easily be added to the Fortran standard.
Maybe like this:

print *, "One million: ",  1_000_000_int32

I don’t think this would break anything because types have to begin with non-digits.

But for reals it might get a bit trickier:

print *, 3_141.59_e-3

This could be 3141.59 of type e minus 3

However, trailing underscores should simply be forbidden.

6

As far as I know it will break existing codes. If an integer kind is equal, for example, to 4, you can write: 1234_4.
Meaning it is an integer constant with an integer kind of 4.

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