Designated initializers in C

C99 lets you name the members and elements you are initializing.

struct Settings {
    int time_limit;
    int editor_mode;
    const char *theme;
};

struct Settings defaults(void) {
    struct Settings s = {.time_limit = 60, .theme = "default"};
    return s;
}

int sparse_sum(void) {
    int weights[8] = {[0] = 5, [3] = 10, [7] = 1};
    int total = 0;
    for (int i = 0; i < 8; i++) {
        total += weights[i];
    }
    return total;
}

How it works

1. Naming a field makes the initializer survive a reordering.
2. Anything not named is zero-initialized.
3. Array designators skip ahead, leaving the gaps at zero.

Keywords and builtins used here

• Settings
• char
• const
• for
• int
• return
• struct
• void

The run, in numbers

Lines

19

Characters to type

333

Tokens

111

Three-star pace

90 tpm

At the three-star pace of 90 tokens a minute, this run takes about 74 seconds.

Type this snippet

Step 3 of 4 in Values & storage, step 29 of 35 in Language basics.

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