[Python-Dev] Rationale for sum()'s design?

Greg Ewing greg.ewing at canterbury.ac.nz
Tue Mar 15 00:20:07 CET 2005

Guido van Rossum wrote:

> But I think the logical consequence of your approach would be that
> sum([]) should raise an exception rather than return 0, which would be
> backwards incompatible. Because if the identity element has a default
> value, the default value should be used exactly as if it were
> specified explicitly.

In that case I would argue in favour of keeping it the
way it is, since...

> currently sum([1,1], 40) equals 42.

...seems quite reasonable to me. Or at least as reasonable
as anything else.

Greg Ewing, Computer Science Dept, +--------------------------------------+
University of Canterbury,	   | A citizen of NewZealandCorp, a	  |
Christchurch, New Zealand	   | wholly-owned subsidiary of USA Inc.  |
greg.ewing at canterbury.ac.nz	   +--------------------------------------+

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