Question

The following code is in Haskell. How would I write similar function in C#?

squareArea xs = [pi * r^2 | r <- xs]

Just to clarify… above code is a function, that takes as input a list containing radius of circles. The expression calculates area of each of the circle in the input list.

I know that in C#, I can achieve same result, by looping thru a list and calculate area of each circle in the list and return a list containing area of circles. My question is… Can the above code be written in similar fashion in C#, perhaps using lambda expressions or LINQ?

Answer 1

Using Enumerable:

IEnumerable<double> SquareArea(IEnumerable<int> xs)
{
    return from r in xs select Math.PI * r * r;
}

or

IEnumerable<double> SquareArea(IEnumerable<int> xs)
{
    return xs.Select(r => Math.PI * r * r);
}

which is very close to Haskell’s

squareArea xs = map (\r -> pi * r * r) xs