Sexp::Matcher
Matches any atom (non-Sexp).
examples:
s(:a) / s{ s(atom) } #=> [s(:a)] s(:a, s(:b)) / s{ s(atom) } #=> [s(:b)]
Satisfied when o is an atom.
o
# File lib/sexp.rb, line 1137 def satisfy? o !(o.kind_of? Sexp) end