是否可以使用 WinHugs 打印 Haskell 中的所有约简？

发布于 2024-07-10 20:41:34 字数 257 浏览 9 评论 0原文

我编写了以下函数..并使用 WinHugs 执行

teneven =  [x | x <- [1..10], even x]

我的输出：

Main> teneven
[2,4,6,8,10] :: [Integer] 
(63 reductions, 102 cells)

是否有办法打印所有缩减..以便我可以了解 WinHugs 内部发生的核心评估？

原文

I have written the following function.. and executed using WinHugs

teneven =  [x | x <- [1..10], even x]

My output:

Main> teneven
[2,4,6,8,10] :: [Integer] 
(63 reductions, 102 cells)

is there anyway to print all the reductions.. so I can learn the core evaluation happening inside WinHugs?

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微暖i 2024-07-17 20:41:34

一些想法：

调试命令行选项（您可以在 Hugs 中使用 :set +d 设置）提供了丰富的信息，但非常冗长，并且不会向您显示 Haskell 语法的减少。
尝试Haskell Tracer。我只是在一个简单的程序上尝试了一下，效果非常酷。不过，我不在 Windows 上，我不知道让它运行起来有多困难。这可能相当困难，这很遗憾，因为它很酷并且本质上就是您想要的。如果您确实运行了它，您可以从 Hat 获取类似以下信息：
<前><代码>主要 = {IO}
十偶 = [2,4,6,8,10]
_foldr (\..) [1,2,3,4,5,6,7,8, ...] [] = [2,4,6,8,10]
(\..) 1 [2,4,6,8,10] = [2,4,6,8,10]
(\..) 2 [4,6,8,10] = [2,4,6,8,10]
(\..) 3 [4,6,8,10] = [4,6,8,10]
(\..) 4 [6,8,10] = [4,6,8,10]
(\..) 5 [6,8,10] = [6,8,10]
(\..) 6 [8,10] = [6,8,10]
(\..) 7 [8,10] = [8,10]
(\..) 8 [10] = [8,10]
(\..) 9 [10] = [10]
(\..) 10 [] = [10]
那里的 lambda 是偶数。此外，如果您愿意，Hat 还可以跟踪 foldr 的调用以及其他内部调用；默认情况下，它不会这样做。

Some ideas:

The debug command-line option (which you can set with :set +d in Hugs) is informative, but is very verbose and does not show you the reductions in Haskell syntax.
Try Hat - the Haskell Tracer. I just tried it on a simple program and it's pretty cool. I'm not on Windows, though, and I don't know how difficult it would be to get it running. It's likely fairly difficult, which is a shame since it's cool and essentially what you want. If you do get it running, you can get something like this information from Hat:
```
main = {IO}
teneven = [2,4,6,8,10]
_foldr (\..) [1,2,3,4,5,6,7,8, ...] [] = [2,4,6,8,10]
(\..) 1 [2,4,6,8,10] = [2,4,6,8,10]
(\..) 2 [4,6,8,10] = [2,4,6,8,10]
(\..) 3 [4,6,8,10] = [4,6,8,10]
(\..) 4 [6,8,10] = [4,6,8,10]
(\..) 5 [6,8,10] = [6,8,10]
(\..) 6 [8,10] = [6,8,10]
(\..) 7 [8,10] = [8,10]
(\..) 8 [10] = [8,10]
(\..) 9 [10] = [10]
(\..) 10 [] = [10]
```
The lambda there is even. Also, if you want, Hat can trace into calls of foldr and other internal calls; by default, it doesn't do that.

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雨巷深深 2024-07-17 20:41:34

这里有一些使用 Debug.Trace 和 Hugs.Observe 的示例。

import Debug.Trace
fact :: Integer -> Integer
fact 0 = trace "fact 0 ->> 1" 1
fact n = trace ("fact " ++ show n) (n * fact (n-1))


import Hugs.Observe
fact :: Integer -> Integer
fact 0 = observe "fact 0" 1
fact n = observe "fact n" (n *  fact (n-1))

希望这可以帮助您了解如何使用 WinHungs 打印所有缩减。

Here you have a few examples of the use of Debug.Trace and Hugs.Observe.

import Debug.Trace
fact :: Integer -> Integer
fact 0 = trace "fact 0 ->> 1" 1
fact n = trace ("fact " ++ show n) (n * fact (n-1))


import Hugs.Observe
fact :: Integer -> Integer
fact 0 = observe "fact 0" 1
fact n = observe "fact n" (n *  fact (n-1))

Hope this helps you to figure out how to print all reductions using WinHungs.

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