sizeof.rb

def sizeof(template)
	x = Class.new(Numeric) do
		def to_str; ""; end
		def to_int; 0; end
		# implicit to_f is called only with Numeric subclass
		def to_f; 0.0; end
	end.new
	size = template.scan(/([a-zA-Z][_!]?[<>]?)([0-9]*)/).reduce(0) {|r,(_,n)|
		r + (n.empty?? 1 : n.to_i)
	}
	# p [template, size]
	Array.new(size) { x }.pack(template).size
end