#include <sqlite3ext.h>

SQLITE_EXTENSION_INIT1

static void sub_func(
    sqlite3_context *ctx,
    int argc,
    sqlite3_value **argv
) {
    if (argc != 2) {
        sqlite3_result_null(ctx);
        return;
    }

    int a = sqlite3_value_int(argv[0]);
    int b = sqlite3_value_int(argv[1]);

    sqlite3_result_int(ctx, a - b);
}

int sqlite3_subext_init(
    sqlite3 *db,
    char **pzErrMsg,
    const sqlite3_api_routines *pApi
) {
    SQLITE_EXTENSION_INIT2(pApi);

    return sqlite3_create_function(
        db,
        "sub",
        2,
        SQLITE_UTF8 | SQLITE_DETERMINISTIC,
        0,
        sub_func,
        0,
        0
    );
}