The scope is as you would expect. The perhaps surprising thing is that the default value is only calculated once and reused, so each time you call the function you get the same list, not a new list initialized to []. The list is stored in f.__defaults__ (or f.func_defaults in Python 2.) def f(a, L=[]): … Read more
Performance-wise, let’s try concrete examples: public void Method1() { foreach(int i in Enumerable.Range(0, 10)) { int x = i * i; StringBuilder sb = new StringBuilder(); sb.Append(x); Console.WriteLine(sb); } } public void Method2() { int x; StringBuilder sb; foreach(int i in Enumerable.Range(0, 10)) { x = i * i; sb = new StringBuilder(); sb.Append(x); Console.WriteLine(sb); … Read more
In the 2.12 release of Gradle, compileOnly was added to give similar functionality to provided scope. There is a difference in what happens in the test classpath. Here is relevant quote and snippet from the release notes: You can now declare dependencies to be used only at compile time in conjunction with the Java plugin. … Read more
The zero initialization is specified in the standard as default zero initialization/value initialization for builtin types, primarily to support just this type of case in template use. Note that this behavior is different from a local variable such as int x; which leaves the value uninitialized (as in the C language that behavior is inherited … Read more
Go performs pointer escape analysis. If the pointer escapes the local stack, which it does in this case, the object is allocated on the heap. If it doesn’t escape the local function, the compiler is free to allocate it on the stack (although it makes no guarantees; it depends on whether the pointer escape analysis … Read more
UPDATE: This question was the subject of my blog in September 2014. Thanks for the great question! There is considerable debate on this question even within the compiler team itself. First off, it’s wise to understand the rules. A public member of a class or struct is a member that is accessible to anything that … Read more
The most common and recommended scenario (for the server side validation in Java serlvets/JSP world) is setting some error message as a request attribute (in the request scope) and then outputting this message in a JSP using Expression Language (see the example below). When the error message is not set – nothing will be shown. … Read more
This is 90% a duplicate of Return local String as a slice (&str), see that for multiple other solutions. There’s one extra possibility since this is all in one function: You can declare a variable for the String and only set it when you need to allocate. The compiler (obliquely) suggests this: consider using a … Read more
Yes, that is prohibited. Just as otherwise you cannot declare variables of differing types in one declaration statement (edit: modulo the declarator modifiers that @MrLister mentions). You can declare structs for (struct { int a = 0; short b = 0; } d; d.a < 10; ++d.a, ++d.b ) {} C++03 code: for (struct { … Read more