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The \spadtype{None} domain is not very useful for interactive
work but it is provided nevertheless for completeness of the
\Language{} type system.
\xtc{
Probably the only place you will ever see it is if you enter an
\index{list!empty}
empty list with no type information.
}{
\spadcommand{[]}
}
\xtc{
Such an empty list can be converted into an empty list
of any other type.
}{
\spadcommand{[] :: List Float}
}
\xtc{
If you wish to produce an empty list of a particular
type directly, such as \spadtype{List NonNegativeInteger}, do it this way.
}{
\spadcommand{[]\$List(NonNegativeInteger)}
}
