How do I compose Linq Expressions? ie Func>, Exp>, Exp>>

Question

I\'m creating a Validator class. I\'m attempting to implement the Linq SelectMany extension methods for my validator to be able to compose

Answer 1

The equivalent of Haskell's function composition operator

(.) :: (b->c) -> (a->b) -> (a->c)
f . g = \ x -> f (g x)

would in C# probably be something like

static Expression> Compose(
    Expression> f,
    Expression> g)
{
    var x = Expression.Parameter(typeof(A));
    return Expression.Lambda>(
        Expression.Invoke(f, Expression.Invoke(g, x)), x);
}

Is this what you're looking for?

Example:

Compose(y => y.ToString(), x => x + 1).Compile()(10); // "11"