declaration – Page 3 – Make Me Engineer

How does the Java array argument declaration syntax “…” work?

October 5, 2022 by Tarik

I believe this was implemented in Java 1.5. The syntax allows you to call a method with a comma separated list of arguments instead of an array. public static void main(String… args); main(“this”, “is”, “multiple”, “strings”); is the same as: public static void main(String[] args); main(new String[] {“this”, “is”, “multiple”, “strings”}); http://today.java.net/article/2004/04/13/java-tech-using-variable-arguments http://download.oracle.com/javase/1.5.0/docs/guide/language/varargs.html

Variable definition inside switch statement

October 5, 2022 by Tarik

According to the C standard (6.8 Statements and blocks), emphasis mine: 3 A block allows a set of declarations and statements to be grouped into one syntactic unit. The initializers of objects that have automatic storage duration, and the variable length array declarators of ordinary identifiers with block scope, are evaluated and the values are … Read more

Why does “extern const int n;” not work as expected?

October 4, 2022 by Tarik

It’s because const implies internal linkage by default, so your “definition” isn’t visible outside of the translation unit where it appears. In this case, by far the best solution is to put the declaration (extern int const n;) in a header file, and include that in both a.cpp and b.cpp. The linkage is determined by … Read more

What is the ‘open’ keyword in Swift?

October 1, 2022 by Tarik

open is a new access level in Swift 3, introduced with the implementation of SE-0117 Allow distinguishing between public access and public overridability It is available with the Swift 3 snapshot from August 7, 2016, and with Xcode 8 beta 6. In short: An open class is accessible and subclassable outside of the defining module. … Read more

Compiler error when declaring a variable inside if condition and no curly braces

August 31, 2022 by Tarik

Because the language spec says so: http://docs.oracle.com/javase/specs/jls/se7/html/jls-6.html A declaration introduces an entity into a program and includes an identifier (§3.8) that can be used in a name to refer to this entity. A declared entity is one of the following: … A local variable, one of the following: * A local variable declared in a … Read more

What does “default” mean after a class’ function declaration?

August 8, 2022 by Tarik

It’s a new C++11 feature. It means that you want to use the compiler-generated version of that function, so you don’t need to specify a body. You can also use = delete to specify that you don’t want the compiler to generate that function automatically. With the introduction of move constructors and move assignment operators, … Read more

How to declare variable and use it in the same Oracle SQL script?

August 7, 2022 by Tarik

There are a several ways of declaring variables in SQL*Plus scripts. The first is to use VAR, to declare a bind variable. The mechanism for assigning values to a VAR is with an EXEC call: SQL> var name varchar2(20) SQL> exec :name := ‘SALES’ PL/SQL procedure successfully completed. SQL> select * from dept 2 where … Read more

How to initialize a vector in C++ [duplicate]

July 24, 2022 by Tarik

With the new C++ standard (may need special flags to be enabled on your compiler) you can simply do: std::vector<int> v { 34,23 }; // or // std::vector<int> v = { 34,23 }; Or even: std::vector<int> v(2); v = { 34,23 }; On compilers that don’t support this feature (initializer lists) yet you can emulate … Read more

Spiral rule and ‘declaration follows usage’ for parsing C and C++ declarations

July 21, 2022 by Tarik

You just have to build it up in steps. char *X(); // X =~ (*(*a[N])()) Function returning char* char *(*Y())(); // Y =~ (*a[N]) Function returning pointer to function returning char*. In a declaration, just as in an expression (declaration follow usage), postfix [] has a higher precedence that unary * so *a[N] is equivalent … Read more

Why is adding attributes to an already instantiated object allowed?

July 15, 2022 by Tarik

A leading principle is that there is no such thing as a declaration. That is, you never declare “this class has a method foo” or “instances of this class have an attribute bar”, let alone making a statement about the types of objects to be stored there. You simply define a method, attribute, class, etc. … Read more