Description
Currently the standard says that any value writing with exponents |exp|>99 shall be written:
(sec. 10.6.1.2.2 of Fortran 03 standard)
99 < |exp| < 1000 +-z1z2z3
This is just horrible.
Basically all parsers of fortran output needs to have a check whether the exponent (currently D or E) are in the field, or whether there is a +- between numbers to figure out if it is an exponent.
I would propose that exponent specifiers are always written.
Note Gfortran is currently standard conforming and will not write the exponent when |exp| > 99... :(
For readers, the only work-around for consistent writing of E is a format like this:
?w.dE3with w=d+8 for full details. This has the side-effect of writing lots of zeros for small numbers, but at least you'll consistently get an easy parseable number...
This was also pointed out in #226:
...
While you're at this, consider also deprecating or deleting0.10+009(with no E or D) as a conforming option for the output of(Ew.d)(noEe). I can't find an implementation that emits it, and it may be an truly dead aspect of the language.
Originally posted by @klausler in #226 (comment)
For reference, here is a test code:
program test
integer, parameter :: dp = 8
real(dp) :: v = 1.23456789123456789123456789e-123_dp
write(*,'("|",G24.16,"|")') v
write(*,'("|",E24.16,"|")') v
write(*,'("|",G24.16E3,"|")') v
write(*,'("|",E24.16E3,"|")') v
write(*,'("|",G24.16,"|")') -v
write(*,'("|",E24.16,"|")') -v
write(*,'("|",G24.16E3,"|")') -v
write(*,'("|",E24.16E3,"|")') -v
end programGfortran 12.3 gives this output:
| 0.1234567891234568-122|
| 0.1234567891234568-122|
| 0.1234567891234568E-122|
| 0.1234567891234568E-122|
| -0.1234567891234568-122|
| -0.1234567891234568-122|
|-0.1234567891234568E-122|
|-0.1234567891234568E-122|