|defv "==" deff

{ ==f ==a a len ==l
  l {
    0 a *
    1 l range { a * f * } each
    } { "fold on empty array" die }
  ? *
} /fold deff

{ ==f _ len ==l l dearray l 1 sub f rep } /foldshort deff

{ ==f { f fold } } /enfold deff

[ 1 2 3 ]
_ |add fold dump
_ |add foldshort dump
_ |add enfold * dump
--