'unsigned variable: value' C++

Question

I am dealing with Ternary Search Tree and I encountered a different thing in ternary search tree node structure:

struct Node {
    char data;

    // True if this character is last character of one of the words
    unsigned isEndOfString: 1;

    struct Node *left, *eq, *right;
};

It is compliled with both C++11 and older versions. I wonder what this unsigned isEndOfString: 1 means? How it is different from bool isEndOfString = true ? What type this statement refers actually and when it is convenient to use such syntax?

http://en.cppreference.com/w/cpp/language/bit_field – user657267 Aug 12 '14 at 07:28 — user657267, Aug 12 '14 at 07:28

score 2 · Accepted Answer · answered Aug 12 '14 at 07:29

2

It is a bit field of size 1. So isEndOfString is a single bit whose value is either 0 or 1.

Basically it allows you here to store a boolean flag in a single bit, minimizing the memory footprint of Node.

Note that bitfields are inherited from C.

answered Aug 12 '14 at 07:29

quantdev

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Thanks! Can you tell me also the `unsigned` by default is `unsigned char` or `unsigned int`? – Kaidul Aug 12 '14 at 07:35
`unsigned` is `unsigned int` by default in standard C++ – quantdev Aug 12 '14 at 07:37

'unsigned variable: value' C++

1 Answers1