在Eclipse中看堆gcmv使用的堆数量？(Amount used heap looking at gcmv in eclipse?)

 虽然我不确定你要用你的函数实现什么，但它不会停止的原因是因为你在无限列表上进行映射并且没有理由停止它。 
 
 无限列表源于您对iterate的使用： 
 
 
 
 lst = (Data.List.iterate id ([1], g_second)) 
 
 
 你在那里做的是创建一个无限列表，其中包含无限数量的元组值([1], g_second) 。 这似乎是一个逻辑错误 - 元组列表没有变化; 每个元素都是相同的，无穷大。 要清楚，您正在构建的列表如下所示： 
 
[([1], g_second), ([1], g_second), ([1], g_second), ([1], g_second)...]
 
 g_second是不变的，永远不会有理由进行评估，所以它实际上是被丢弃的。 
 
 如果您使用take或takeWhile类的东西，则可以强制该无限列表停止并返回已知数量的元素。 但是，通过在此声明中使用map ： 
 
map (\x -> (last (fst x))) lst
 
 你所做的就是从元组中提取值1并永远重复它。 
 
 由于您丢弃g_second并且从不使用g_first ，因此您的函数等效于以下内容： 
 
rp :: RandomGen g => g -> ([Int], g)
rp g = (repeat 1 , snd (next g))

While I'm not exactly sure what you're trying to achieve with your function, the reason it doesn't stop is because you're mapping over an infinite list and giving it no reason to stop.
 
The infinite list originates in your use of iterate:
 
 
 
lst = (Data.List.iterate id ([1], g_second))
 
 
What you've done there is create an infinite list which contains an infinite number of the tuple value ([1], g_second). That seems like a logic error - that list of tuple has no variation; every element is the same, to infinity. To be clear, this list you are building looks like this:
 
[([1], g_second), ([1], g_second), ([1], g_second), ([1], g_second)...]
 
g_second is unchanging and never gets a reason to evaluate, so it is, in essence, discarded.
 
If you were to use something like take or takeWhile, you could force that infinite list to stop and return a known number of elements. However, by using map in this statement:
 
map (\x -> (last (fst x))) lst
 
All you are doing is pulling the value 1 out of the tuple and repeating it forever.
 
And since you discard g_second and never use g_first, your function is equivalent to the following:
 
rp :: RandomGen g => g -> ([Int], g)
rp g = (repeat 1 , snd (next g))