Hi Jerry,

I think for the current testcases, I like the patch – the question is 
only what's about:

   ',3' as input for 'comma'   (or '.3' as input for 'point')

For 'point' – 0.3 is read and ios = 0 (as expected)
But for 'comma':
* GCC 12 reads nothing and has ios = 0.
* GCC 13/mainline has an error (ios != 0 – and reads nothing)
* GCC with your patch: Same result: ios != 0 and nothing read.

Expected: Same as with ','/'comma' – namely: read-in value is 0.3.
→ https://godbolt.org/z/4rc8fz4sT for the full example, which works with 
ifort, ifx and flang

* * *

Can you check and fix this? It looks perfectly valid to me to have 
remove the '0' in the floating point numbers '0.3' or '0,3' seems to be 
permitted – and it works for '.' (with 'point') but not for ',' (with 
'comma').

F2023's "13.10.3.1 List-directed input forms" refers to "13.7.2.3.2 F 
editing", which states:

"The standard form of the input field [...] The form of the mantissa is 
an optional sign, followed by a string of one or more digits optionally 
containing a decimal symbol."

The latter does not require that the digit has to be before the decimal 
sign and as for output, it is optional, it is surely intended that ",3" 
is a valid floating-point number for decimal='comma'.

* * *

I extended the testcase to check for this – see attached diff. All 
'point' work, all 'comma' fail.

Thanks for working on this!

Tobias