Mathematically, it makes much more sense to return 0.

Yes but logically (and mathematically too), the sum of an undefined list ought to be an undefined value, don't you think?

sum() returning undef or 0 helps discern whether the argument list passed to it was an empty one or not. 

$ perl -MList::Util=sum -Wle 'printf "sum returns [%s]", sum()'
Use of uninitialized value in printf at -e line 1.
sum returns []

$ perl -MList::Util=sum -Wle 'printf "sum returns [%s]", sum(undef)
Use of uninitialized value in subroutine entry at -e line 1.
sum returns [0]

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perl -e '$,=$",$_=(split/\W/,$^X)[y[eval]]]+--$_],print+just,another,split,hack'er

In reply to Re: List::Util::sum() and empty lists... by Firefly258
in thread List::Util::sum() and empty lists... by blazar

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