Re: [DOCS] to_char(): 'FM' also suppresses *trailing* zeroes - Mailing list pgsql-docs

Erwin Brandstetter <brsaweda@gmail.com> writes:
> In Table 9-27. "Template Pattern Modifiers for Numeric Formatting" it says:
> FM | prefix fill mode (suppress leading zeroes and padding blanks) | FM9999

> In fact, 'FM' also suppresses *trailing* zeroes after the comma. To fix,
> this might be changed to:
>    suppress insignificant zeroes and padding blanks

Not necessarily.  A bit of experimentation says that it also matters
whether you use "0" or "9" as the format character:

So it appears to me that the bit you point out is flat out backwards;
what FM actually suppresses is trailing zeroes not leading zeroes.

I'm tempted to propose that in table 9-26, we need to write

        9       digit position (can be dropped if insignificant)

        0       digit position (cannot be dropped, even if insignificant)

and then in 9-27 say

        FM      fill mode: suppress trailing zeroes and padding spaces

Also, in between those two tables, I see

      * 9 results in a value with the same number of digits as there are
        9s. If a digit is not available it outputs a space.

This seems outright wrong per the above examples, and in any case is not
very useful since it doesn't explain the difference from "0".  Perhaps
rewrite as

        * 0 specifies a digit position that will always be printed,
          even if it contains a leading/trailing zero.  9 also specifies
          a digit position, but if it is a leading zero then it will be
          replaced by a space, while if it is a trailing zero and fill mode
          is specified then it will be deleted.