lisp_ruby.rb

def lisp_eval(x)
	if x == '1'
		1
	elsif x == '#t'
		true
	else
		list = x.gsub(" ", '').chars
		parser(list)
	end
end

def parser(list)
	return list.first.to_i unless list.join('').match(/\(.*\)/)
		sub_list = list[1..-2]
		if sub_list.join('').match(/\(.*\)/)
			start_idx = sub_list.index('(')
			end_idx = sub_list.length - sub_list.reverse.index(')')
			val = parser(sub_list[start_idx..end_idx])
			before = sub_list[0..start_idx]
			after = sub_list[end_idx..sub_list.length]
			sub_list = (before << val) + after
		end
		operator = sub_list.shift
		sub_list.reduce { |x,y| x.to_i.send(operator, y.to_i)}
end