我想下载一堆用ISO-8601日期命名的文件.使用bash + GNU coreutils有一种简单的方法吗？(或者让wget/curl自动生成列表的一些技巧,但我发现这不太可能)
与此问题类似,但不限于工作日:如何使用bash中提供的工具生成一系列非周末日期？.我想有一种更简单的方法可以在没有这种限制的情况下做到这一点.
还与如何在bash上生成随机数据的日期范围有关,但不限于一年.
是否可以从fundep类创建类型族实例？例如，假设我有课
\n\nclass A a b | a -> b\n有一些实例（导入外部库）并希望为该类型系列创建所有相应的实例
\n\ntype family A' a :: *\n这样A' a ~ biff A a b，无需从外部源手动复制和修改实例。
我该怎么做（如果可能的话）？
\n\n迄今为止我最有希望的尝试，
\n\nclass A' a where\n type A'_b a :: *\n\ninstance forall a b. A a b => A' a where\n type A'_b a = b\n给出错误消息
\n\n The RHS of an associated type declaration mentions \xe2\x80\x98b\xe2\x80\x99\n All such variables must be bound on the …我刚刚阅读了使用await和async关键字在C#5.0中处理异步函数的新方法.从等待的C#参考考试:
private async Task SumPageSizesAsync()
{
// To use the HttpClient type in desktop apps, you must include a using directive and add a
// reference for the System.Net.Http namespace.
HttpClient client = new HttpClient();
// . . .
Task<byte[]> getContentsTask = client.GetByteArrayAsync(url);
byte[] urlContents = await getContentsTask;
// Equivalently, now that you see how it works, you can write the same thing in a single line.
//byte[] urlContents = await client.GetByteArrayAsync(url); …我知道我可以使用 nix-env 搜索 Haskell 包
nix-env -f '<nixpkgs>' -qaP -A haskellPackages name_of_package
但这很慢而且没有缓存。如果我尝试使用新命令，nix search所有 Haskell 包都被隐藏。
$ nix search aeson
error: no results for the given search term(s)!
是否可以使用新nix search命令搜索 Haskell 包？如果是这样，如何？
编辑：我在这个irc 日志中发现了一些关于这个的讨论，但我不太明白这些建议在实践中的含义。具体这部分：
20:49 <duairc> How do I make nix search include haskellPackages?
20:52 <ottidmes> duairc: you might try and call recurseIntoAttrs on haskellPackages
20:52 <rain1> thanks
20:52 <LnL> rain1: nix-env -f '<nixpkgs>' -qaP -A haskellPackages
20:54 <gchristensen> duairc: ^
20:54 <duairc> …我已经构建了一个小型的UDP/protobuf发送器和接收器.我花了一个上午的时间试图找出protobuf解码产生错误的原因,结果却发现发送器(Spoke.hs)发送的数据不正确.
用于unpack将Lazy.ByteStrings转换为网络包将发送的字符串的代码.我unpack在Hoogle 找到了.它可能不是我正在寻找的功能,但它的描述看起来合适:"O(n)将ByteString转换为字符串."
Spoke.hs产生以下输出:
chris@gigabyte:~/Dropbox/haskell-workspace/hub/dist/build/spoke$ ./spoke
45
45
["a","8","4a","6f","68","6e","20","44","6f","65","10","d2","9","1a","10","6a","64","6f","65","40","65","78","61","6d","70","6c","65","2e","63","6f","6d","22","c","a","8","35","35","35","2d","34","33","32","31","10","1"]
虽然wireshark告诉我数据包中的数据是:
0a:08:4a:6f:68:6e:20:44:6f:65:10:c3:92:09:1a:10:6a:64:6f:65:40:65:78:61:6d:70:6c:65:2e:63:6f:6d:22:0c:0a:08:35:35:35:2d:34:33:32:31:10
Spoke.hs和Wireshark的长度(45)是相同的.
Wireshark缺少最后一个字节(值0x01),中心值流不同(在Wireshark中大一个字节).
"65","10","d2","9"在Spoke.hs和65:10:c3:92:09Wireshark中.
由于0x10是DLE,它让我感到震惊,可能正在进行一些转义,但我不知道为什么.
我对Wireshark有多年的信任,只有几十个小时的Haskell经验,所以我认为这是错误的代码.
任何建议赞赏.
-- Spoke.hs:
module Main where
import Data.Bits
import Network.Socket -- hiding (send, sendTo, recv, recvFrom)
-- import Network.Socket.ByteString
import Network.BSD
import Data.List
import qualified Data.ByteString.Lazy.Char8 as B
import Text.ProtocolBuffers.Header (defaultValue, uFromString)
import Text.ProtocolBuffers.WireMessage (messageGet, messagePut)
import Data.Char (ord, intToDigit)
import Numeric
import Data.Sequence ((><), fromList)
import AddressBookProtos.AddressBook
import AddressBookProtos.Person
import AddressBookProtos.Person.PhoneNumber
import AddressBookProtos.Person.PhoneType
data UDPHandle = …我有一个执行长时间计算的程序,其结果显示为绘图.我目前正在使用Chart-0.14.我想显示部分结果,并在计算过程中更新.
Graphics.Rendering.Chart.Gtk.updateCanvas :: Renderable a -> DrawingArea -> IO Bool似乎这样做,但我没有找到任何方法从剧情中获得DrawingArea.该函数renderableToWindow :: Renderable a -> Int -> Int -> IO ()不返回任何内容(并且在窗口关闭之前它不会返回).
我想做类似以下的事情:
main = do
drawingArea = forkRenderableToWindow (toRenderable $ plotLayout $
plot [0,0.1..10] sin "sin(x)") 640 480
updateCanvas (toRenderable $ plotLayout $ plot [0,0.1..10] sin "sin(x)") drawingArea
我该怎么做？我是否需要在Graphics.Rendering.Chart.Gtk一个版本中重新实现函数,DrawingArea以及以某种方式返回(我将如何执行此操作？forkIO？)立即返回而不关闭窗口？