Taken from Dart’s language guide What is soundness? Soundness is about ensuring your program can’t get into certain invalid states. A sound type system means you can never get into a state where an expression evaluates to a value that doesn’t match the expression’s static type. For example, if an expression’s static type is String, … Read more
Let’s decompose it one-by-one. Box Box<T> is a pointer to heap-allocated T. We use it here because trait objects can only exist behind pointers. Trait objects In Box<Fn() + Send + ‘static>, Fn() + Send + ‘static is a trait object type. In future, it will be written Box<dyn (Fn() + Send + ‘static)> to … Read more
Assuming the question is about Go, e.g. var _ foo.RequiredInterface = myType{} // or &myType{} or [&]myType if scalar as a TLD will check that for you at compile time.
If you only deal with integers, you can use str.isdigit(): Return true if all characters in the string are digits and there is at least one character, false otherwise. [row for row in listOfLists if row[x].isdigit()] Or if negative integers are possible (but should be allowed): row[x].lstrip(‘-‘).isdigit() And of course this all works only if … Read more
ALTER TABLE <table> SET TBLPROPERTIES(‘EXTERNAL’=’TRUE’) Note: EXTERNAL and TRUE need to caps or it will not work
You can use filterNotNull Here is a simple example: val a: List<Int?> = listOf(1, 2, 3, null) val b: List<Int> = a.filterNotNull() But under the hood, stdlib does the same as you wrote /** * Appends all elements that are not `null` to the given [destination]. */ public fun <C : MutableCollection<in T>, T : … Read more
This restrictions was made because java(language) has it: interface A {} // Error:(7, 26) java: a type variable may not be followed by other bounds <T1, T2 extends T1 & A> void test() {} And we suppose that this forbidden also in bytecode level. I dig into it and seems like it is allowed, and … Read more
The way sum is defined, the return value is open-ended; more than one type can implement the trait Sum<i32>. Here’s an example where different types for a are used, both of which compile: #[derive(Clone, Copy)] struct Summer { s: isize, } impl Summer { fn pow(&self, p: isize) { println!(“pow({})”, p); } } impl std::iter::Sum<i32> … Read more
You have to use a generic function where the parameter is only used for type information so you cast it to T: func doSomething<T>(_ a: Any, myType: T.Type) { if let a = a as? T { //… } } // usage doSomething(“Hello World”, myType: String.self) Using an initializer of the type T You don’t … Read more
You could create a wrapper around a string and pass that around: class GUID { private str: string; constructor(str?: string) { this.str = str || GUID.getNewGUIDString(); } toString() { return this.str; } private static getNewGUIDString() { // your favourite guid generation function could go here // ex: http://stackoverflow.com/a/8809472/188246 let d = new Date().getTime(); if (window.performance … Read more