Wouldn't it be nice to have the following definitions for Sum and Product in order to get the sum resp. the product of a list/vector?
Unprotect[Product];
Product[a_] := Times @@ a
Protect[Product];
Unprotect[Sum];
Sum[a_] := Plus @@ a
Protect[Sum];
\[Sum]{a, b, c, d} == Sum[{a, b, c, d}] == Sum[e, {e, {a, b, c, d}}] ==
Plus @@ {a, b, c, d} == a + b + c + d
\[Product]{a, b, c, d} == Product[e, {e, {a, b, c, d}}] ==
Product[{a, b, c, d}] == Times @@ {a, b, c, d} == a*b*c*d
True
True
