A desperate attempt to comment one place where we do conversions.

  if (dec >= NOT_FIXED_DEC)

  {

    /*

      Let's try to pretty print a floating point number. Here we use

      '%-*.*g' conversion string:

        '-' stands for left-padding with spaces, if such padding will take

      place

        '*' is a placeholder for the first argument, field_length, and

      signifies minimal width of result string. If result is less than

      field length it will be space-padded. Note, however, that we'll not

      pass spaces to Field_string::store(const char *, ...), due to

      strcend in the next line.

        '.*' is a placeholder for DBL_DIG and defines maximum number of

      significant digits in the result string. DBL_DIG is a hardware

      specific C define for maximum number of decimal digits of a floating

      point number, such that rounding to hardware floating point

      representation and back to decimal will not lead to loss of

      precision. I.e if DBL_DIG is 15, number 123456789111315 can be

      represented as double without precision loss.  As one can judge from

      this description, chosing DBL_DIG here is questionable, especially

      because it introduces a system dependency.

        'g' means that conversion will use [-]ddd.ddd (conventional) style,

      and fall back to [-]d.ddde[+|i]ddd (scientific) style if there is no

      enough space for all digits.

      Maximum length of result string (not counting spaces) is (I guess)

      DBL_DIG + 8, where 8 is 1 for sign, 1 for decimal point, 1 for

      exponent sign, 1 for exponent, and 4 for exponent value.

      XXX: why do we use space-padding and trim spaces in the next line?

    */

    sprintf(to,"%-*.*g",(int) field_length,DBL_DIG,nr);

    to=strcend(to,' ');

  }