[Python-Dev] Re: [Python-checkins] CVS: python/dist/src/Lib calendar.py,1.17,1.18

[Rob W. W. Hooft]

Just checking my E-mail coming back from holidays, I see:

  diff -C2 -r1.17 -r1.18
  *** calendar.py 2000/08/30 14:01:28     1.17
  --- calendar.py 2000/10/09 12:42:04     1.18
  ***************
  *** 55,60 ****
    def leapdays(y1, y2):
        """Return number of leap years in range [y1, y2).
  !        Assume y1 <= y2 and no funny (non-leap century) years."""
  !     return (y2+3)/4 - (y1+3)/4

    def weekday(year, month, day):
  --- 55,62 ----
    def leapdays(y1, y2):
        """Return number of leap years in range [y1, y2).
  !        Assume y1 <= y2."""
  !     y1 -= 1
  !     y2 -= 1
  !     return (y2/4 - y1/4) - (y2/100 - y1/100) + (y2/400 - y1/400)

    def weekday(year, month, day):

I am worried about the use of "-=" here. The code basically says: "if the
arguments are mutable numeric types, I'd like to modify them in place". In
c.l.py it has been stressed multiple times that "-=" is not the same as
"=   -". I think this is clearly a place where "=   -" is preferable over
"-=". Even though you might think people will always call this with 
python integers, you can never be sure enough.

Rob

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