First of all… yes its a good way of doing it, it’s clean, small form and easy to read & understand… the caveat of course is “Unless you later want to unsubscribe”. I believe Jon Skeet pointed out before that “the specification explicitly doesn’t guarantee the behaviour either way when it comes to equivalence of … Read more
The one thing you could test for is code object equality: >>> x = lambda x: x >>> y = lambda y: y >>> x.__code__.co_code ‘|\x00\x00S’ >>> x.__code__.co_code == y.__code__.co_code True Here the bytecode for both functions is the same. You’ll perhaps need to verify more aspects of the code objects (constants and closures spring … Read more
Lambdas in C# do not have types, until they are used in a context that casts them to a delegate or Expression type. That’s why you cannot do the following: var x = () => “some lambda”; You might enjoy Eric Lippert’s Series on Lambda Expressions vs Anonymous Methods Lambda vs Anon – Part One … Read more
Capturing a local variable is actually performed by “hoisting” the local variable into an instance variable of a compiler-generated class. The C# compiler creates a new instance of the extra class at the appropriate time, and changes any access to the local variable into an access of the instance variable in the relevant instance. So … Read more
So to start with, the first expression can only possibly call the first overload. It is not a valid expression for a Func<Task> because there is a code path that returns an invalid value (void instead of Task). () => while(true) is actually a valid method for either signature. (It, along with implementations such as … Read more
Well, FindAll copies the matching elements to a new list, whereas Where just returns a lazily evaluated sequence – no copying is required. I’d therefore expect Where to be slightly faster than FindAll even when the resulting sequence is fully evaluated – and of course the lazy evaluation strategy of Where means that if you … Read more
The Expression API supports this in .NET 4.0, but sadly the C# compiler doesn’t add any extra candy to support. But the good news is that you can trivially take a “get” expression (which the C# compiler can write) and re-write it as a “set” expression. And even better; if you don’t have .NET 4.0, … Read more
You can’t nest method references. You can use lambda expressions instead: return Comparator .comparing(l->l.getCourse().getTeacher().getAge(), Comparator.reverseOrder()) .thenComparing(l->l.getCourse().getStudentSize()); Without the need for reverse order it’s even less verbose: return Comparator .comparing(l->l.getCourse().getTeacher().getAge()) .thenComparing(l->l.getCourse().getStudentSize()); Note: in some cases you need to explicitly state the generic types. For example, the code below won’t work without the <FlightAssignment, LocalDateTime> before comparing(…) … Read more
§5.1.2/6 says: The closure type for a lambda-expression with no lambda-capture has a public non-virtual non-explicit const conversion function to pointer to function having the same parameter and return types as the closure type’s function call operator. The value returned by this conversion function shall be the address of a function that, when invoked, has … Read more
FINAL UPDATE: The bug has been fixed in C# 5. Apologies again for the inconvenience, and thanks for the report. Original analysis: I can reproduce the problem with the command-line compiler. It certainly looks like a bug. It’s probably my fault; sorry about that. (I wrote all of the lambda-to-delegate conversion checking code.) I’m in … Read more