Re: RFC 76 (v1) Builtin: reduce

[Ariel Scolnicov]

Perl6 RFC Librarian <[EMAIL PROTECTED]> (but actually it was Damian
Conway) writes:

> If the original list has no elements, C<reduce> immediately returns C<undef>.

I like everything except this part.  Reducing an empty list should be
an error.

Returning undef (or anything else, really) breaks the algebraic
equivalence that

            f((reduce \&f, LIST), $x) eq (reduce \&F, LIST, $x)

Since this is the single most important property of reduce (indeed, it 
is the *only* property of reduce), I don't see what we get by breaking 
it.

Also, the RFC should specify that the function is always evaluated in
a scalar context (for things to make sense).

-- 
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