language-implementation

问题 Is there a way to see the code behind a JavaScript's method? Not a javascript method from the website's .html or .js files, but JavaScript's internal methods. For example: How can I see how JavaScript calculates the offsetTop of an element? 回答1: JavaScript is implemented by the browser, so it depends on the browser . Google's browser, Chrome , is closed-source not open-source. Which means that you can't view their source code, including their implementation of JavaScript. But , Chrome's

问题 The Perl array is an abstract data type. What's the internal mechanism for the Perl array? Is it implemented with dynamic array or linked list? Since the array elements have random access, I would assume a dynamic array of pointers, or references to scalars make sense. However, with shift and unshift operation at the head of array, would the array have to move all its elements with these operations? sound inefficient to me. Any thought? 回答1: Have a look at this: http://www.perlmonks.org/?node

问题 I recently used the shift operators in Java and noticed that the >> operator does not have the same meaning as >> in C. In Java >> is Signed shift that keeps the first bit at the same value. In Java the equivalent to C shift is the >>> operator. The left shift operator ( << ) is the same as in C and just shifts ignoring the first bit. The things I wondered are Why make this change? Why is the notation not consistent so >> and << are signed shift and >>> and <<< are unsigned? Is there any use

问题 I recently used the shift operators in Java and noticed that the >> operator does not have the same meaning as >> in C. In Java >> is Signed shift that keeps the first bit at the same value. In Java the equivalent to C shift is the >>> operator. The left shift operator ( << ) is the same as in C and just shifts ignoring the first bit. The things I wondered are Why make this change? Why is the notation not consistent so >> and << are signed shift and >>> and <<< are unsigned? Is there any use

问题 I've been told that if I'm coding in ANSI-C to declare in the order that the variables will be used, assert that pointers are not null and that indices are within bounds, and to initialize just before usage of the variable. If I declare a const can I initialize it after a block of assertions and code ? In Java final initializations must occur at declaration, yet is it consistent through ANSI-C implementations that I can initialize a const once but not necessarily at the time of declaration ?

问题 In java an AtomicMarkableReference can be used to update atomically an object reference along with a mark bit. The javadoc states: Implementation note: This implementation maintains markable references by creating internal objects representing "boxed" [reference, boolean] pairs. This is true according to what can be seen in the java 8 source code of the class: package java.util.concurrent.atomic; public class AtomicMarkableReference<V> { private static class Pair<T> { final T reference; final

问题 I wanted to write some educational code in Haskell with Unicode characters (non-Latin) in the identifiers. (So that the identifiers look nice and natural for speakers of a natural language other than English which is not using the Latin characters in its writing.) So, I set out for finding an appropriate Haskell implementation that would allow this. But where is this feature specified in the language specification? How would I refer to this feature when looking for a conforming implementation

问题 I have been trying to understand the internal implementation of java.util.HashMap and java.util.HashSet . Following are the doubts popping in my mind for a while: Whats is the importance of the @Override public int hashcode() in a HashMap/HashSet? Where is this hash code used internally? I have generally seen the key of the HashMap be a String like myMap<String,Object> . Can I map the values against someObject (instead of String) like myMap<someObject, Object> ? What all contracts do I need

问题 I am just trying to understand why all fields defined in an Interface are implicitly static and final . The idea of keeping fields static makes sense to me as you can't have objects of an interface but why they are final (implicitly)? Any one knows why Java designers went with making the fields in an interface static and final ? 回答1: An interface can't have behavior or state because it is intended to specify only an interaction contract, no implementation details. No behavior is enforced by

问题 According to the docs: inspect.currentframe() Return the frame object for the caller’s stack frame. CPython implementation detail: This function relies on Python stack frame support in the interpreter, which isn’t guaranteed to exist in all implementations of Python. If running in an implementation without Python stack frame support this function returns None. How is it that only this function is marked as "implementation-dependent"? If this function doesn't work, wouldn't similar functions,