On Tue, Jun 14, 2011 at 06:51, jerry DeLisle<jvdelisle@charter.net> wrote:
It should be easy to implement:
After the switch between F and E editing, we just need to shift the
decimal point and decrement the exponent. No new rounding is required,
because we keep the number of significant digits.
OK, after a little bit of experimentation, I have arrived at the updated
patch attached.
This has been regression tested and passes all test cases I am aware of. I
also have included a new test case gcc/testsuite/gfortran.dg/fmt_g.f90.
OK for trunk?
I have reviewed your patch, and I noticed that you placed the
digit-shifting code quite at the top of output_float(), where the
final value of e is not even known. Due to rounding, e can be modified
after this point, so your code will generate invalid output in some
cases, for example:
print "(-2PG0)", nearest(0.1d0, -1.0d0) ! 1.0000000000000000E+001
expected .0099999999999999992E+001
Please put the code where at belongs, after the switch between F and E
editing (based on the final value of e).
The same applies to the scale factor in general, e.g.
print "(-2pg12.3)", 0.096 ! 1.00E+01 expected 0.001E+02
print "(-1pg12.3)", 0.0996 ! 1.00E+00 expected 0.010E+01
print "(-2pg12.3)", 0.09996 ! 1.00E+01 expected 0.100
print "(-1pg12.3)", 0.09996 ! 1.00E+00 expected 0.100
print "(1pg12.3)", 0.099996 ! 1.000E-01 expected 0.100
print "(2pg12.3)", 0.099996 ! 10.00E-02 expected 0.100
print "(-2pg12.3)", 999.6 ! 0.100E+04 expected 0.001E+06
print "(-1pg12.3)", 999.6 ! 0.100E+04 expected 0.010E+05
print "(1pg12.3)", 999.6 ! 0.100E+04 expected 9.996E+02
print "(2pg12.3)", 999.6 ! 0.100E+04 expected 99.96E+01
Please revise your code to fix this. A working approach I have outlined in
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48906#c28
and an (alpha) implementation is here:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48906#c31