Operators vs Functions in C/C++

Question

Someone recently asked me the difference between a C++ standard operator (eg new,delete,sizeof) and function (eg tan,free, malloc). By "standard" I mean those provided by default by the compiler suite, and not user defined . Below were the answers I gave, though neither seemed satisfactory.

(1) An operator doesn't need any headers to be included to use it : Eg you can have a call to new without including any headers. However, a function (say free() ) does need headers included, compulsorily.

(2) An operator is defined as such (ie as a class operator) somewhere in the standard headers. A function isn't.

Can you critique these answers and give me a better idea of the difference?

Answer 1

Operators are keywords with a fixed syntax. Those which can be overloaded might vary a bit in syntax, but that's within the boundaries. The new operator is still spelled new , even when overloaded and the syntax of invoking it is always the same.

Function names are identifiers , which can be almost arbitrary. There's no syntactic reason you couldn't do away with malloc() and use

bool my_fancy_alloc(void*& memory, unsigned char size, bool zero_it);

instead. (Mark: There are other reasons, though. Like your fellow-workers' sanity.)

Answer 2

(1) isn't strictly true. typeid is an operator, but its use requires that you include <typeinfo> .

My answer would simply be that operators are defined as such. :: doesn't necessarily need to be considered an operator, for instance, but the standard says it is, and so it is.

If you're looking for a more verbose answer, I would go on to mention that operators mostly do not look like functions. And those that do [ sizeof and typeid ] don't act as functions; their operands are not evaluated at runtime.

Answer 3

An operator is compiled to a sequence of instructions by the compiler.

When the code calls a function , it has to jump to a separate piece of code

Answer 4

运算符具有特殊语法，例如，您可以使用new （或+ ）而不在运算符名称后面的括号中放置参数。

Answer 5

An operator and function are conceptually same. Both of them take some values as input and return some as output. They only difference is there syntax.

Answer 6

我的理解函数名称是goto运算符的表示，在跳转到特定代码位置后，应用程序可以执行一个到多个工作单元，另一方面操作员执行实际的工作单元。