也许是一个时髦的标题,但我遇到以下问题:
给定一个类型列表(a * b) list,我想创建一个带有类型的新列表(a * b list) list.一个例子:
给定列表let testList = [(1,"c");(2,"a");(1,"b")],我的函数应该返回[(1, ["c";"b"]; (2, ["a"])].
我有以下内容,但我有点坚持如何继续:
let rec toRel xs =
match xs with
| (a,b)::rest -> (a,[b])::toRel rest
| _ -> []
如果我在 Visual Studio Code 中的 fsx 中输入以下内容
let longString = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum."
Alt …
在视图(AudioView.xaml)中,我编写了以下代码
<Slider
Name="AudioSlider"
Width="200"
Height="23"
Grid.Column="0"
IsSelectionRangeEnabled="True"
IsSnapToTickEnabled="True"
Maximum="{Binding Path=TotalAudioPlayingSeconds, Mode=OneTime}"
Minimum="0"
Style="{StaticResource CustomStyleForSlider}"
Thumb.DragCompleted="{Binding AudioSliderChangedCommand}"
TickFrequency="1"
Value="{Binding Path=AudioPosition}"/>
注意:还有文件AudioView.xaml.cs.
在视图模型class(AudioViewModel.cs)中,我定义了以下属性
public event DragCompletedEventHandler AudioSliderChangedCommand;
并在视图模型类(AudioViewModel.cs)的构造函数中
this.AudioSliderChangedCommand = new DragCompletedEventHandler(OnAudioSliderChanged);
在编译期间,我收到以下错误
错误8 DragCompleted ="{Binding AudioSliderChangedCommand}"无效.{Binding AudioSliderChangedCommand}不是有效的事件处理程序方法名称.只有生成的或代码隐藏类上的实例方法才有效.
我想将一个合理的文本放入文本块但是给我一个错误.为什么？我能解决吗？
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
<TextBlock Height="220"
HorizontalAlignment="Left"
Margin="102,174,0,0"
Name="textBlock1"
Text="TextBlock sdfg asfgbfgb adf ab afg g "
TextAlignment="Justify"
VerticalAlignment="Top"
Width="255" />
</Grid>
我收到了一个错误报告,似乎来自以下代码:
public class AnimationChannelCollection : ReadOnlyCollection<BoneKeyFrameCollection>
{
private Dictionary<string, BoneKeyFrameCollection> dict =
new Dictionary<string, BoneKeyFrameCollection>();
private ReadOnlyCollection<string> affectedBones;
// This immutable data structure should not be created by the library user
internal AnimationChannelCollection(IList<BoneKeyFrameCollection> channels)
: base(channels)
{
// Find the affected bones
List<string> affected = new List<string>();
foreach (BoneKeyFrameCollection frames in channels)
{
dict.Add(frames.BoneName, frames);
affected.Add(frames.BoneName);
}
affectedBones = new ReadOnlyCollection<string>(affected);
}
public BoneKeyFrameCollection this[string boneName]
{
get { return dict[boneName]; }
}
}
这是读取字典的调用代码:
public override Matrix GetCurrentBoneTransform(BonePose pose) …我想用Map初始化一个递归函数.要声明具有值的只读字典,我们可以这样做:
let dictionary1 = dict [ (1, "a"); (2, "b"); (3, "c") ]
现在,我想创建一个空字典.怎么实现呢？
我正在寻找像:
let dictionary1 = {} // <- ok this is js
let (stuff, dictionary2) = parseRec("whatever", dictionary1)
我不认为我的标题是准确的,所以只需转到代码.
namespace Fobaizer
{
template <typename T, typename C>
static T GetItemFromContainer(const C &container) {
T item = container[0]; // do something. 0 or iterator
return item;
}
}
例:
MyClass myClass = Fobaizer::GetItemFromContainer<MyClass, vector<MyClass>(myVector);
要么
MyClass myClass = Fobaizer::GetItemFromContainer<MyClass, deque<MyClass>(myDeque);
这里C是任何容器,如std::deque或std::vector.我搜索没有任何lib的C98解决方案(boost,QT等)
事实上,我正在寻找像IEnumerableC#这样的东西.
任何的想法 ？
谢谢.
Debug.Log("Hello there!");
print("Hello there");
这两个语句在控制台上显示相同的输出,那有什么区别？
当我将 a 分配Dictionary<int, HashSet<int>>给 a 时IDictionary<int, IEnumerable<int>>，出现以下错误：
编译错误（第 27 行，第 9 列）：无法将类型“System.Collections.Generic.Dictionary>”隐式转换为“System.Collections.Generic.IDictionary>”。存在显式转换（您是否缺少演员表？）
错误很明显。缺少演员表。为什么我需要演员阵容？Dictionary<T,U>执行IDictionary<T,U>和HashSet<T>执行IEnumerable<T>。
using System;
using System.Linq;
using System.Collections.Generic;
public class Program
{
public class A
{
public IDictionary<int, IEnumerable<int>> D { get; set; }
public IEnumerable<int> H { get; set; }
}
public static void Main()
{
var hashSet = new HashSet<int>{1,2,1};
var a = new A { H = hashSet };
PrintCollection(a.H);
var d = new …