C++ syntax error: string must be quoted with double quotes, how to deal with it?

In the C language, the string data type is a common data type that is often used to store and process text data. In C programming, strings need to be declared and processed using quotes. Strings can be declared using double or single quotes. When working with strings, declaring string constants using single quotes will cause a compilation error. This article will explore string declaration and processing in C and explain how to solve the problem of strings having to be quoted using double quotes.

String declaration and use in C

In C, strings can be represented by char arrays, also known as string arrays. C supports two types of strings: C-style strings and strings from the STL string library.

C-style string is essentially an array of character type, consisting of a series of characters. Each element in a string array is of type character and can be declared with single quotes. In C-style strings, the end of the string is always terminated by a null character ''.

For example, the following is code that declares a C-style string containing the string "Hello World":

char greeting[] = "Hello World";

The string in the STL string library is encapsulated by the class string object. String objects in the STL string library can be used in programs like ordinary variables. For example, the following is the code for an STL string object declaration:

#include <string>
using namespace std;

string greeting = "Hello World";

When processing strings, you can use string functions. There are many functions in C specifically for string processing. For example, the following are some commonly used string functions:

• strlen(): Returns the length of a given string (excluding the trailing null character ).
• strcpy(): Copy one string to another string.
• strcat(): Concatenates two strings.
• strcmp(): Compares two strings to see if they are the same.

The problem that strings must be quoted using double quotes

In C programming, using single quotes to declare string constants will cause compilation errors. Therefore, when declaring a string, you must quote the string using double quotes. For example, the following code uses single quotes when declaring a string, which will cause a compilation error:

char greeting = 'Hello World';

When you run the above code, you will get the following error message:

error: multi-character character constant [-Werror=multichar]

To solve this problem, you must Change single quotes to double quotes. Rewrite the code as follows:

char greeting[] = "Hello World";

In this way, the problem of declaring strings is solved. In C language, it is very critical to use correct quotation marks to declare strings, otherwise it will cause syntax errors.

Conclusion

In C, string is one of the important data types and is often used to store and process text data. When working with strings, you must use the correct quotes to declare the string, otherwise a compilation error will result. In C-style strings, the end of the string is always terminated by a null character ''. String objects in the STL library can be used in programs like ordinary variables, providing rich operations on strings. C has many built-in string functions to facilitate developers to process strings.

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