A function with signature Num a => a is expected to work for any type in the class Num. The implementation 5.0 :: Double just works for one type, not for all types of the class, so the compiler complains. An example of a generic function would be: square :: (Num a) => a -> … Read more
Here’s my favorite implementation of binary search. It’s useful not only for finding the element but also for finding the insertion index. Details about assumed sorting order (ascending or descending) and behavior with respect to equal elements are controlled by providing a corresponding predicate (e.g. { $0 < x } vs { $0 > x … Read more
You need to do this… Type unknown = ((ObjectHandle)tmp).Unwrap().GetType(); By the way, this is a little confusing because if you call Activator.CreateInstance on a type in your current assembly… Activator.CreateInstance(typeof(Foo)) …the object is not wrapped and the original code works fine.
You can bind to interfaces by telling wpf explicitly that you are binding to an interface field: (Please note that ViewModelBase is simply a base-class that implements the INotifyPropertyChanged interface) public class Implementation : ViewModelBase, IInterface { private string textField; public string TextField { get { return textField; } set { if (value == textField) … Read more
The answer is: you don’t need to provide overloads for ALL the numeric types, just for Double and Decimal. All others (except maybe some very unusually large ones) will be automatically converted to these. Not a base class but in fact that was the red herring. The base class System.ValueType doesn’t help much as it … Read more
“What are the differences between Integer and Int?” Integer is just an alias for java.lang.Integer. Int is the Scala integer with the extra capabilities. Looking in Predef.scala you can see this the alias: /** @deprecated use <code>java.lang.Integer</code> instead */ @deprecated type Integer = java.lang.Integer However, there is an implicit conversion from Int to java.lang.Integer if … Read more
It is the most generally used for library purpose. The main principe behind Opaque type in c is to use data though its pointer in order to hide data handling implementation. Since the implementation is hidden, you can modify the library without recompiling any program which depend on it (if the interface is respected) eg: … Read more
Since IPv4 addresses are 4 byte long, you could use an INT (UNSIGNED) that has exactly 4 bytes: `ipv4` INT UNSIGNED And INET_ATON and INET_NTOA to convert them: INSERT INTO `table` (`ipv4`) VALUES (INET_ATON(“127.0.0.1”)); SELECT INET_NTOA(`ipv4`) FROM `table`; For IPv6 addresses you could use a BINARY instead: `ipv6` BINARY(16) And use PHP’s inet_pton and inet_ntop … Read more
Yes, this is standard practice in academic literature. To understand it, it helps to know that the notion of “type” was invented in the 1930s, in the context of lambda calculus (in fact, even earlier, in the context of set theory). Since then, a whole branch of computational logic has emerged that is known as … Read more
int (*getFunc())(int, int) { … } That provides the declaration you requested. Additionally, as ola1olsson notes, it would be good to insert void: int (*getFunc(void))(int, int) { … } This says that getFunc may not take any parameters, which can help avoid errors such as somebody inadvertently writing getFunc(x, y) instead of getFunc()(x, y).