Passing in operators

[Tem]

I have 3 static methods that share almost the same code with only a few
lines where different operators are used.

Is there a way to pass in an operator as a parameter?

pseudo code

Greater() {Base(>)}
Less() {Base(<)}
Equal() {Base(==)}

Base(operator op)
{
....

if(a op b)
....
}

Or another way of doing this?

Tem

[Marc Gravell]

Or another way of doing this?

Depending on what you are doing, you could use a delegate - i.e. a
Func<T,T,bool>; whether this is a good idea (or not) depends on the
scenario... easy enough in C# 3 with lambdas...

public static void Greater() {Base((x,y) =x y);}
public static void Less() {Base((x,y) =x < y);}
public static void Equal() {Base((x,y) =x == y);}

private static void Base(Func<Foo,F oo,boolop)
{
//...
if(op(a,b))
{
//...
}
}

(again: I stress hard to give a great answer without more info)

Marc

[Marc Gravell]

I should also add that for equaility (==, !=) an inequality (<, <=, >,

>=) you can also use EqualityCompare r<T>.Default and

Comparer<T>.Def ault to do a lot, without requiring direct access to
operators (actually it uses IComparable<Tan d IEquatable<T>).

Marc

[Paul E Collins]

"Tem" <te*****@yahoo. comwrote:

I have 3 static methods that share almost the same code with only a
few lines where different operators are used. Is there a way to pass
in an operator as a parameter?

What you can do is pass in a delegate (method pointer) that performs the
desired comparison, e.g.
delegate bool CompareDelegate (int x, int y);
static void Main()
{
CompareDelegate lessThan = delegate(int x, int y) { return x < y; };
CompareDelegate moreThan = delegate(int x, int y) { return x y; };

bool isLess = Compare(2, 5, lessThan); // true
bool isMore = Compare(2, 5, moreThan); // false
}
static bool Compare(int a, int b, CompareDelegate c)
{
return c(a, b);
}
Eq.

[Tem]

Thank you guys for the help. Now I see what delegates are useful for.

"Paul E Collins" <fi************ ******@CL4.orgw rote in message
news:l5******** *************** *******@bt.com. ..

"Tem" <te*****@yahoo. comwrote:

>I have 3 static methods that share almost the same code with only a few
lines where different operators are used. Is there a way to pass in an
operator as a parameter?

What you can do is pass in a delegate (method pointer) that performs the
desired comparison, e.g.
delegate bool CompareDelegate (int x, int y);
static void Main()
{
CompareDelegate lessThan = delegate(int x, int y) { return x < y; };
CompareDelegate moreThan = delegate(int x, int y) { return x y; };

bool isLess = Compare(2, 5, lessThan); // true
bool isMore = Compare(2, 5, moreThan); // false
}
static bool Compare(int a, int b, CompareDelegate c)
{
return c(a, b);
}
Eq.

[Tem]

Can this be written with lambda expressions?

"Paul E Collins" <fi************ ******@CL4.orgw rote in message
news:l5******** *************** *******@bt.com. ..

"Tem" <te*****@yahoo. comwrote:

>I have 3 static methods that share almost the same code with only a few
lines where different operators are used. Is there a way to pass in an
operator as a parameter?

What you can do is pass in a delegate (method pointer) that performs the
desired comparison, e.g.
delegate bool CompareDelegate (int x, int y);
static void Main()
{
CompareDelegate lessThan = delegate(int x, int y) { return x < y; };
CompareDelegate moreThan = delegate(int x, int y) { return x y; };

bool isLess = Compare(2, 5, lessThan); // true
bool isMore = Compare(2, 5, moreThan); // false
}
static bool Compare(int a, int b, CompareDelegate c)
{
return c(a, b);
}
Eq.

[Marc Gravell]

Can this be written with lambda expressions?

yes; I aleady posted a variant using lambdas (although using the
"delegate" version of a lambda*); using an actual Expression is
possible - not sure if it gains much, though (the delegate is likely
to be quicker than reflection from a PropertyInfo).

Whether this is the *best* approach depends largely on the full
scenario.

*=lambdas can be compiled to either a delegate or a System.Expressi on.

Marc