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Near the beginning of Section 2.3 we defined a List informally as “a finite sequence of zero or more atoms or Lists.”
Any forest is a List; for example,
may be regarded as the List
and the corresponding List diagram would be
The reader should review at this point the introduction to Lists given earlier, in particular (3), (4), (5), (6), (7) in the opening pages of Section 2.3. Recall that, in (2) above, the ...