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cannot convert from 'T' to 'sbyte' using Generics

rschaaf
rschaaf asked
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Last Modified: 2008-02-01
Here's my function:

static public void SetMin<T>(ref T a, T b) {  // Invalid - Cannot convert from'T' to sbyte
      a = Math.Min(a, b);
}

Visual Studio 2005 gives the errors:
The best overloaded method match for 'System.Math.Min(sbyte, sbyte)' has some invalid arguments
Argument '1': Cannot convert from 'T' to 'sbyte'
Argument '2': Cannot convert from 'T' to 'sbyte'

Why is this?  If I unwrap this method and declare directly with sbyte, the compiler is fine with it:

static public void SetMin(ref sbyte a, sbyte b) {  // Works fine
      a = Math.Min(a, b);
}
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Commented:
Math.Min has many overloaded methods but all accepts number type parameters.
When compiling your generic function, the compiler doesn't know the type T. There is no way to compile this.

Try this:

static public T GetMin<T>(T a, T b) where T : IComparable
        {
            if (a.CompareTo(b) <= 0)
                return a;
            else
                return b;
        }

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Commented:
I don't know way to do this using Math function, but this one can be used as replacement:

        static public void SetMin<T>(ref T a, T b) where T :IComparable<T>
        {
            a = a.CompareTo(b) < 0 ? a : b;
        }

Commented:
Oops, sorry for duplicated post.

Commented:
Actually, it is not 100% duplicated, because I use IComparable<T> :)

Commented:
True, IComparable<T> is better.
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