CODEWITHSUNDEEP
c++string
tomtclai
tomtclai

Reputation: 333

why is it possible to use 'string' as the name of a variable

I'm a beginner in C++ and I'm doing one of the exercises in Stroustrup's Programming Principles And Practice Using C++. This exercise wants me to experiment with legal and illegal names.

void illegal_names()
{
//    the compiler complains about these which made sense:
//    int double =0;
//    int if =0;
//    int void = 0;
//    int int = 0;
//    int while =0;
//    string int = "hello";
//    
//    however, this is legal and it runs without a problem:
    double string = 0.0;
    cout << string<< endl;

}

My question is, what makes string different than any other types? Are there other types that is special like string?

Upvotes: 0

Views: 1544

Answers (3)

macfij
macfij

Reputation: 3209

in C++ std::string is a defined data type (class), not a keyword. it's not forbidden to use it as variable name. it is not a reserved word. consider a C++ program, which also works:

#include <iostream>

class xxx {
    int x;
public:
    xxx(int x_) : x(x_) {}
    int getx() { return x;}
};

int main()
{
    xxx c(4);
    std::cout << c.getx() << "\n";
    int xxx = 4;  // this works
    std::cout << xxx << "\n";

    return 0;
}

this the same case as with string. xxx is user defined data type and as you can see it is not reserved.
the image below shows list of reserved keywords in c++. enter image description here

Upvotes: 0

Vlad from Moscow
Vlad from Moscow

Reputation: 311010

string is not a keyword so it may be used as an identifier. All other statemenets in the code segment are erroneous because there are used keywords as identifiers.

As for standard class std::string then you can even write in a block scope

std::string string;

In this case the identifier string declared in the block scope will hides type std::string

For example

#include <iostream>
#include <string>

int main() 
{
    std::string string = "Hello, string";
    std::cout << string << std::endl;

    return 0;
}

Upvotes: 0

Logicrat
Logicrat

Reputation: 4468

All of those other names are reserved words in the C++ language. But "string" is not. Even though string is a commonly used data type, it is built out of more basic types and defined in a library which itself is written in C++.

Upvotes: 5

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