我如何用c#优雅地做到这一点?
例如,一个数字可以是1到100之间。
我知道一个简单的if (x >= 1 && x <= 100)就足够了;但是有很多语法糖和新特性不断添加到c# /。Net这个问题是关于更习惯的(一个可以称之为优雅的)写法。
性能不是问题,但请在非O(1)的解决方案中添加性能说明,因为人们可能会复制粘贴建议。
我如何用c#优雅地做到这一点?
例如,一个数字可以是1到100之间。
我知道一个简单的if (x >= 1 && x <= 100)就足够了;但是有很多语法糖和新特性不断添加到c# /。Net这个问题是关于更习惯的(一个可以称之为优雅的)写法。
性能不是问题,但请在非O(1)的解决方案中添加性能说明,因为人们可能会复制粘贴建议。
当前回答
你的意思是?
if(number >= 1 && number <= 100)
or
bool TestRange (int numberToCheck, int bottom, int top)
{
return (numberToCheck >= bottom && numberToCheck <= top);
}
其他回答
像这样的怎么样?
if (theNumber.isBetween(low, high, IntEx.Bounds.INCLUSIVE_INCLUSIVE))
{
}
扩展方法如下(已测试):
public static class IntEx
{
public enum Bounds
{
INCLUSIVE_INCLUSIVE,
INCLUSIVE_EXCLUSIVE,
EXCLUSIVE_INCLUSIVE,
EXCLUSIVE_EXCLUSIVE
}
public static bool isBetween(this int theNumber, int low, int high, Bounds boundDef)
{
bool result;
switch (boundDef)
{
case Bounds.INCLUSIVE_INCLUSIVE:
result = ((low <= theNumber) && (theNumber <= high));
break;
case Bounds.INCLUSIVE_EXCLUSIVE:
result = ((low <= theNumber) && (theNumber < high));
break;
case Bounds.EXCLUSIVE_INCLUSIVE:
result = ((low < theNumber) && (theNumber <= high));
break;
case Bounds.EXCLUSIVE_EXCLUSIVE:
result = ((low < theNumber) && (theNumber < high));
break;
default:
throw new System.ArgumentException("Invalid boundary definition argument");
}
return result;
}
}
因为所有其他答案都不是我发明的,这里只是我的实现:
public enum Range
{
/// <summary>
/// A range that contains all values greater than start and less than end.
/// </summary>
Open,
/// <summary>
/// A range that contains all values greater than or equal to start and less than or equal to end.
/// </summary>
Closed,
/// <summary>
/// A range that contains all values greater than or equal to start and less than end.
/// </summary>
OpenClosed,
/// <summary>
/// A range that contains all values greater than start and less than or equal to end.
/// </summary>
ClosedOpen
}
public static class RangeExtensions
{
/// <summary>
/// Checks if a value is within a range that contains all values greater than start and less than or equal to end.
/// </summary>
/// <param name="value">The value that should be checked.</param>
/// <param name="start">The first value of the range to be checked.</param>
/// <param name="end">The last value of the range to be checked.</param>
/// <returns><c>True</c> if the value is greater than start and less than or equal to end, otherwise <c>false</c>.</returns>
public static bool IsWithin<T>(this T value, T start, T end) where T : IComparable<T>
{
return IsWithin(value, start, end, Range.ClosedOpen);
}
/// <summary>
/// Checks if a value is within the given range.
/// </summary>
/// <param name="value">The value that should be checked.</param>
/// <param name="start">The first value of the range to be checked.</param>
/// <param name="end">The last value of the range to be checked.</param>
/// <param name="range">The kind of range that should be checked. Depending on the given kind of range the start end end value are either inclusive or exclusive.</param>
/// <returns><c>True</c> if the value is within the given range, otherwise <c>false</c>.</returns>
public static bool IsWithin<T>(this T value, T start, T end, Range range) where T : IComparable<T>
{
if (value == null)
throw new ArgumentNullException(nameof(value));
if (start == null)
throw new ArgumentNullException(nameof(start));
if (end == null)
throw new ArgumentNullException(nameof(end));
switch (range)
{
case Range.Open:
return value.CompareTo(start) > 0
&& value.CompareTo(end) < 0;
case Range.Closed:
return value.CompareTo(start) >= 0
&& value.CompareTo(end) <= 0;
case Range.OpenClosed:
return value.CompareTo(start) > 0
&& value.CompareTo(end) <= 0;
case Range.ClosedOpen:
return value.CompareTo(start) >= 0
&& value.CompareTo(end) < 0;
default:
throw new ArgumentException($"Unknown parameter value {range}.", nameof(range));
}
}
}
然后你可以这样使用它:
var value = 5;
var start = 1;
var end = 10;
var result = value.IsWithin(start, end, Range.Closed);
就像其他人说的,使用简单的if。
你应该考虑一下顺序。
e.g
1 <= x && x <= 100
容易读吗
x >= 1 && x <= 100
In C, if time efficiency is crucial and integer overflows will wrap, one could do if ((unsigned)(value-min) <= (max-min)) .... If 'max' and 'min' are independent variables, the extra subtraction for (max-min) will waste time, but if that expression can be precomputed at compile time, or if it can be computed once at run-time to test many numbers against the same range, the above expression may be computed efficiently even in the case where the value is within range (if a large fraction of values will be below the valid range, it may be faster to use if ((value >= min) && (value <= max)) ... because it will exit early if value is less than min).
不过,在使用这样的实现之前,请先对目标机器进行基准测试。在某些处理器上,由两部分组成的表达式可能在所有情况下都更快,因为两个比较可能是独立完成的,而在减法和比较方法中,减法必须在比较执行之前完成。
新花样的老最爱:
public bool IsWithinRange(int number, int topOfRange, int bottomOfRange, bool includeBoundaries) {
if (includeBoundaries)
return number <= topOfRange && number >= bottomOfRange;
return number < topOfRange && number > bottomOfRange;
}