Where can I find the “clamp” function in .NET?

问题

I would like to clamp a value x to a range [a, b]:

x = (x < a) ? a : ((x > b) ? b : x);

This is quite basic. But I do not see a function \"clamp\" in the class library - at least not in System.Math.

(For the unaware to \"clamp\" a value is to make sure that it lies between some maximum and minimum values. If it’s greater than the max value, then it’s replaced by the max, etc.)

回答1:

You could write an extension method:

public static T Clamp<T>(this T val, T min, T max) where T : IComparable<T>
{
    if (val.CompareTo(min) < 0) return min;
    else if(val.CompareTo(max) > 0) return max;
    else return val;
}

EDIT: Extension methods go in static classes - since this is quite a low-level function, it should probably go in some core namespace in your project. You can then use the method in any code file that contains a using directive for the namespace e.g.

using Core.ExtensionMethods

int i = 4.Clamp(1, 3);

.NET Core 2.0

Starting with .NET Core 2.0 System.Math now has a Clamp method that can be used instead:

using System;

int i = Math.Clamp(4, 1, 3);

回答2:

Try:

public static int Clamp(int value, int min, int max)  
{  
    return (value < min) ? min : (value > max) ? max : value;  
}

回答3:

Just use Math.Min and Math.Max:

x = Math.Min(Math.Max(x, a), b);

回答4:

There isn't one, but it's not too hard to make one. I found one here: clamp

It is:

public static T Clamp<T>(T value, T max, T min)
    where T : System.IComparable<T> {
        T result = value;
        if (value.CompareTo(max) > 0)
            result = max;
        if (value.CompareTo(min) < 0)
            result = min;
        return result;
    }

And it can be used like:

int i = Clamp(12, 10, 0); -> i == 10
double d = Clamp(4.5, 10.0, 0.0); -> d == 4.5

回答5:

There isn't one in the System.Math namespace

http://msdn.microsoft.com/en-us/library/system.math_members.aspx

There is a MathHelper Class where it is available for the XNA game studio if that happens to be what you are doing:

http://msdn.microsoft.com/en-us/library/bb197892(v=XNAGameStudio.31).aspx

回答6:

Just sharing Lee's solution with the comments' issues and concerns addressed, where possible:

public static T Clamped<T>(this T value, T min, T max) where T : IComparable<T> {
    if (value == null) throw new ArgumentNullException(nameof(value), "is null.");
    if (min == null) throw new ArgumentNullException(nameof(min), "is null.");
    if (max == null) throw new ArgumentNullException(nameof(max), "is null.");
    //If min <= max, clamp
    if (min.CompareTo(max) <= 0) return value.CompareTo(min) < 0 ? min : value.CompareTo(max) > 0 ? max : value;
    //If min > max, clamp on swapped min and max
    return value.CompareTo(max) < 0 ? max : value.CompareTo(min) > 0 ? min : value;
}

Differences:

Method name uses the appropriate verb tense (ed) to (further) indicate that the value is not clamped in-place, and that, instead, a new value is returned (See @JimBalter's comment).
Does appropriate null check on all inputs (See @JeppeStigNielsen's comment).
Swaps min and max if min > max (See @JeppeStigNielsen's comment).

Limitations: No one-sided clamps. If max is NaN, always returns NaN (See Herman's comment).

回答7:

Using the previous answers, I condensed it down to the below code for my needs. This will also allow you to clamp a number only by its min or max.

public static class IComparableExtensions
{
    public static T Clamped<T>(this T value, T min, T max) 
        where T : IComparable<T>
    {
        return value.CompareTo(min) < 0 ? min : value.ClampedMaximum(max);
    }

    public static T ClampedMinimum<T>(this T value, T min)
        where T : IComparable<T>
    {
        return value.CompareTo(min) < 0 ? min : value;
    }

    public static T ClampedMaximum<T>(this T value, T max)
        where T : IComparable<T>
    {
        return value.CompareTo(max) > 0 ? max : value;
    }
}

回答8:

The below code supports specifying bounds in any order (i.e. bound1 <= bound2, or bound2 <= bound1). I've found this useful for clamping values calculated from linear equations (y=mx+b) where the slope of the line can be increasing or decreasing.

I know: The code consists of five super-ugly conditional expression operators. The thing is, it works, and the tests below prove it. Feel free to add strictly unnecessary parentheses if you so desire.

You can easily create other overloads for other numeric types and basically copy/paste the tests.

Warning: Comparing floating point numbers is not simple. This code does not implement double comparisons robustly. Use a floating point comparison library to replace the uses of comparison operators.

public static class MathExtensions
{
    public static double Clamp(this double value, double bound1, double bound2)
    {
        return bound1 <= bound2 ? value <= bound1 ? bound1 : value >= bound2 ? bound2 : value : value <= bound2 ? bound2 : value >= bound1 ? bound1 : value;
    }
}

xUnit/FluentAssertions tests:

public class MathExtensionsTests
{
    [Theory]
    [InlineData(0, 0, 0, 0)]
    [InlineData(0, 0, 2, 0)]
    [InlineData(-1, 0, 2, 0)]
    [InlineData(1, 0, 2, 1)]
    [InlineData(2, 0, 2, 2)]
    [InlineData(3, 0, 2, 2)]
    [InlineData(0, 2, 0, 0)]
    [InlineData(-1, 2, 0, 0)]
    [InlineData(1, 2, 0, 1)]
    [InlineData(2, 2, 0, 2)]
    [InlineData(3, 2, 0, 2)]
    public void MustClamp(double value, double bound1, double bound2, double expectedValue)
    {
        value.Clamp(bound1, bound2).Should().Be(expectedValue);
    }
}

来源：https://stackoverflow.com/questions/2683442/where-can-i-find-the-clamp-function-in-net

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