Running with the Dynamic Language Runtime in C#.NET

Making Code 3/9 in C#.NET Running with the Dynamic Language Runtime

The runtime helps the compiler to construct code in the compiled assembly that will make a lot of choices dynamically The code block at the end of the preceding section is an example of the simplest kind The DLR assisted in the creation of IRONRuby, which makes it possible to code in Ruby the current hot dynamic language right in Visual Studio Of course, because the DLR enables C# to take on dynamic language features, much that you can do in Ruby you can now do in C#

Ruby takes advantage of its dynamic roots in its implementation of the Trabb Pardo-Knuth algorithm Don t be put off by the name this is just a straightforward problem that can be solved by computer code The program needs to read 11 numbers from an input device in our case, the console s ReadLine method It stores them in an array Then, it processes the array backward starting from the last entered value with some function If the value doesn t exceed some arbitrary threshold, it prints the result The program looks like this in Ruby:

Programming Dynamically!

def main Arraynew(11) { getsto_i }reverseeach do |x| y = f(x) puts #{x} #{(y>400) TOO LARGE : y} end end end

This isn t a Ruby book, and that fact isn t lost on me Nonetheless, this is the best dynamic language that I can use for an example bar none Two functions are defined: f and main Main accepts 11 numbers from the console and then moves them to an integer array (that s what getsto_i does) For each value in the array, it sets y equal to f(x) and then sees if it is higher than our arbitrary value If so, it prints TOO LARGE ; otherwise, it prints the number Why is being dynamic important for this algorithm It isn t You could do it all statically typed The dynamic bit does have an impact, though First, f(x) doesn t care what x is The program assumes that whatever comes in gets changed to an integer at getsto_i, but the function itself is case agnostic This is good and bad, because if we do happen to give it a string or some other type, it will fail The array itself isn t typed, either This can have benefits, because it is possible to drop a differently typed value in there if you know you are just going to write it to the screen

Dynamic C#

Of course, C# now has similar features, right We should be able to do the same thing! Yes, in fact, we can Here s the code:

static dynamic f(dynamic x) { return (MathSqrt(x) + 50 * MathPow(x, 30)); } static void Main(string[] args) { dynamic[] array = new Array[11]; for (int i = 0; i < 11; i++) { array[i] = ConsoleReadLine(); } for (int i = 10; i>=0; i--) {

dynamic y = f(array[i]); if (y > 4000) { ConsoleWriteLine(stringFormat( {0} TOO LARGE , i)); }else{ ConsoleWriteLine( {0} : {1} , i, array[1]); } } ConsoleReadKey(); }

Line for line, the application does the same thing as the Ruby code, albeit longer I kept the names the same so it was easier to follow Because I had to use for loops to handle the integrators, it made the body of the program quite a bit beefier Figure 1-2 shows what the program looks like when it runs

But why use the dynamic type here Clearly we could have just used double for this Use of dynamic just made the program easier to create Try changing the array to an array of double, like this:

Double[] array = new Double[11];