I have noticed in the libraries that are often methods that take multiple parameters and each parameter can take a number of different types. A simple example, BigDecimal#add method has two parameters: a.add(b,n), where a is BigDecimal, b needs to be compatible with BigDecimal and n needs to be compatible with Fixnum. In other words it is possible that b and n can be one of [NotNull]BigDecimal/*!*/, [NotNull]BigInteger/*!*/, int, double and object. This leads to an implementation question.
Initially it seemed sensible to abstract out the conversion of these types - except perhaps the best case ([NotNull]BigDecimal/*!*/ and int) - into a helper method and then have just: public static BigDecimal/*!*/ Add(CodeContext/*!*/ context, BigDecimal/*!*/ self, BigDecimal/*!*/ b, int n) ... and public static BigDecimal/*!*/ Add(CodeContext/*!*/ context, BigDecimal/*!*/ self, object b, object n) ... In the second method you convert the parameters to the correct types and pass them back to the first method. This is basically what happens in the current implementation of many of the Socket library methods. This provides a single place of conversion, which is particularly helpful given the BigDecimal class has lots of methods that take this form that will all use this conversion. It makes the code readable and doesn't create masses of overloads for the class. After thinking about this for a bit I started to wonder about performance. This style of method does not allow performance tricks in the DLR to benefit the code. If you have the type lookup inside the methods then that gets called every single time those methods are called. The other implementation idea then is to create method overloads for all the permutations of the parameter types. This leads to a massive increase in methods but could provide better performance at run time; It may happen already, or it certainly could in the future, that the DLR is able to calculate the method required from the calling code (i.e. Ruby code) and generate IL that will call that method directly during execution. Therefore the type lookup only needs to happen once. This would make a huge difference in some of the BigDecimal functionality where you may well be doing complex calculations and expecting a reasonable level of performance. The trouble with this is that it is a right pain to code up and leaves lots of room for programmer error. Also I imagine that this will lead to even longer start-up times for IronRuby, which I suspect is going to be the major performance issue going forward, what with all the code generation and JIT compilation. Any one got thoughts on this? Pete
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