通过15个小例子学习ruby

以下都是从国外网站翻译过来，自己学习的时候总结了一下，希望对大家学习ruby有所帮助。

1. Problem: “Display series of numbers (1,2,3,4, 5….etc) in an infinite loop. The program should quit if someone hits a specific key (Say ESCAPE key).” 

 解决方案

i = 0
loop { print "#{i+=1}, " }

     虽然是一个很简单的问题，但我想着想着却觉得这个问题很有意思，原文中也没有给出很完美的答案，不知道谁有好的解决方法。

2. Problem: “Fibonacci series, swapping two variables, finding maximum/minimum among a list of numbers.”

解决方案

#Fibonacci series
Fib = Hash.new{ |h, n| n < 2 ? h[n] = n : h[n] = h[n - 1] + h[n - 2] }
puts Fib[50]

#Swapping two variables
x,y = y,x

#Finding maximum/minimum among a list of numbers
puts [1,2,3,4,5,6].max
puts [7,8,9,10,11].min

 

语法知识：

1.Hash。Hash在实例话的时候可以在new里边接受一个参数值，或者一个模块，它实际上不是hash对象的一个值，仅当在hash操作的时候找不到这个值对应的项的时候返回。

2.交换两个变量。

3.查询数组里最大最小的值，有专门的API。

 3. Problem: “Accepting series of numbers, strings from keyboard and sorting them ascending, descending order.”

 解决方案

a = []
loop { break if (c = gets.chomp) == ‘q’; a << c }
p a.sort
p a.sort { |a,b| b<=>a }
loop循环，及break的应用
从键盘读入字符 gets.chomp
将一项插入到数组 a << c
对于数组的正序和倒序的排序。
vars = %w{D V Rho Mu}

vars.each do |var|
  print "#{var} = "
  val = gets
  eval("#{var}=#{val.chomp}")
end

reynolds = (D*V*Rho)/Mu.to_f

if (reynolds < 2100)
  puts "Laminar Flow"
elsif (reynolds > 4000)
  puts "Turbulent Flow"
else
  puts "Transient Flow"
end
vars = { "d" => nil, "v" => nil, "rho" => nil, "mu" => nil }

begin
  vars.keys.each do |var|
    print "#{var} = "
    val = gets
    vars[var] = val.chomp.to_i
  end

  reynolds = (vars["d"]*vars["v"]*vars["rho"]) / vars["mu"].to_f
  puts reynolds

  if (reynolds < 2100)
    puts "Laminar Flow"
  elsif (reynolds > 4000)
    puts "Turbulent Flow"
  else
    puts "Transient Flow"
  end

  print "Do you want to calculate again (y/n)? "
end while gets.chomp != "n"