gistfile1.rb

#!/usr/bin/env ruby
# vim: noet


capitals = {
	"England" => "london",
	"France"  => "paris",
	"Germany" => "berlin",
	"Spain"   => "madrid",
	"Italy"   => "rome",
}


def normalize(items)
	
	# calculate the total of all weights
	total = (items.inject(0) do |total, item|
		total += item[1]
	end).to_f
	
	# create a new array with the
	# weights replaced with ratios
	items.collect do |str, weight|
		[str, (weight/total)]
	end
end


# Returns a random string from an
# array of [string, weight] pairs
def pick(items)
	choice = rand
	
	normalize(items).each do |str, weight|
		return str if choice <= weight
		choice -= weight
	end
end


# build a separate array to keep track of weights for each country,
# so we can prioritize questions that the user often gets wrong
weights = capitals.keys.collect do |country|
	[country, 1]
end


# keep playing until this script
# is terminated (with ctrl+c)
while true
	choice = pick(weights)
	
	# ask a question, get an answer
	print "What is the capital of #{choice.upcase}? "
	if gets.strip.downcase == capitals[choice].downcase
		puts "Correct!"
		
		# correct answer; increase the weight of all others,
		# causing this country to appear less frequently
		weights.each_index do |n|
			weights[n][1] += 1 unless\
				weights[n][0] == choice
		end
		
	else
		puts "The answer is: #{capitals[choice].upcase}"
		
		# wrong answer, so increase the weight of
		# this country, so it appears more often
		weights.each_index do |n|
			weights[n][1] += 1 if\
				weights[n][0] == choice
		end
	end
	
	puts "Weights are now: #{weights.inspect}"
	puts # blank line
end