Chaos Project

def auc
   its = ac = x2 = x1 = nil
	puts 'start point of domain:'
	x1 = gets
	x1 = x1.to_i
	puts 'end point of domain:'
	x2 = gets
	x2 = x2.to_i
	puts 'accuracy:'
	ac = gets	
	ac = ac.to_i
	puts 'solving...'
	w = 1
	area = 0
	last_area = 0
	i1 = 0
	x = x1
	loop do
		area = 0
		a=(1.0/(10)**i1)
		(((x2 - x1) / a).floor).times { |i2|
			fx = yield(x + (i2 * a))
			box = fx * a
			area += box
		}
		unless i1 == 0
			difference = area - last_area

			last_area = area
			break if difference.abs <= (1*(10**(-ac)))
		end
		i1 += 1
		puts 'iteration: ' + i1.to_s + 'Compleate...'
	end
	puts  '-----------------------------------------------------------'
	puts 'area: ' + area.to_s
	puts 'iterations: ' + (i1 + 1).to_s
	puts  '-----------------------------------------------------------'
	puts 'type \'exit\' to close, or press enter to continue with another function'
	s = gets
	case s.upcase
	when /\AEXIT/
		exit
	else
		start_program
	end
end

def start_program
	puts '=============================================='
	puts 'Welcome to the area under a curve calculus solver'
	puts 'to use simply type you function in below and then follow the prompts'
	puts 'for exsample '
	puts '((-x)**2) + 2'
	puts 'Would be the function x^2 + 2'
	puts 'the solver only recognises certain symbols for mathmatical'
	puts 'operations, see the below for conversions'
	puts 'make sure to use \"X\" when typeing in your equation'
	puts '* >> Multiplication'
	puts '** >> raise to a power '
	puts '/ >> Division '
	puts 'Math.cos(x) >> Cosine of x '
	puts 'Math.sin(x) >> Sine of x '
	puts 'Math.tan(x) >> Tangent of x '
	puts 'Math.log(x) >> Ln of x '
	puts 'Math.log10(x) >> Log base 10 of x '
	puts 'Math.sqrt(x) >> Square root of x '
	puts '(x).abs >> Absolute value of '
	puts 'Math::E >> e '
	puts 'Math::PI >> pi '
	puts '=============================================='
	puts 'type \'exit\' to close'
	puts 'type your function below'
	no_input = true
	while no_input == true
		s = gets
		case s.upcase
		when ''
			puts 'ERROR Please enter a function'
		when /\AEXIT/
			puts 'Closing...'
			exit
		else
			no_input  = false
		end
	end
	f = 'auc{|x| ' + s.to_s + '}'
	begin
		eval(f)
	rescue 
		puts 'ERROR'
		puts $!.message
	end
end

begin
	start_program
end