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# sentence generator
class SentGen
def initialize(syntax)
@syntax = syntax
end
def each_tree(sym, limit)
generate_from_sym(sym, limit) {|_, tree|
yield tree
}
nil
end
def each_string(sym, limit)
generate_from_sym(sym, limit) {|_, tree|
yield [tree].join('')
}
nil
end
def generate_from_sym(sym, limit, &b)
return if limit < 0
if String === sym
yield limit, sym
else
rules = @syntax[sym]
rules.each {|rhs|
if rhs.length == 1 || rules.length == 1
limit1 = limit
else
limit1 = limit-1
end
generate_from_rhs(rhs, limit1, &b)
}
end
nil
end
def generate_from_rhs(rhs, limit)
return if limit < 0
if rhs.empty?
yield limit, []
else
generate_from_sym(rhs[0], limit) {|limit1, child|
generate_from_rhs(rhs[1..-1], limit1) {|limit2, arr|
yield limit2, [child, *arr]
}
}
end
nil
end
end
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