Read the first collection element.
C++: Access index zero only after establishing that the collection is nonempty.
#include <iostream>
#include <string>
#include <array>
#include <iomanip>
#include <cstdlib>
int main() {
std::array<int, 3> items{5, 10, 15};
if (!items.empty()) std::cout << items.front() << "\n";
}Expected output EXAMPLE
5
Details
Save as snippet.cpp; compile with g++ -std=c++17 -Wall -Wextra snippet.cpp -pthread -o snippet, then run ./snippet.
Tested on Ubuntu 24.04.5 LTS · · g++ (Ubuntu 13.3.0-6ubuntu2~24.04.1) 13.3.0 · g++ 4:13.2.0-7ubuntu1
Test inputs, results and environment
The exact published code ran in a dedicated Linux test container with prepared inputs. Unprivileged snippet process, external networking disabled, read-only root filesystem, and a fresh temporary working directory. Fixtures and output records are isolated from the application database. Testing covers this example and its stated checks, not every input, operating system, or runtime version. The Linux container shares its host's kernel; this is not a native Windows test.
- Architecture / host kernel
- x86_64 / 6.18.54.1-microsoft-standard-WSL2
- Snippet identity / locale
- uid=65534, gid=65534 (unprivileged) / C.UTF-8
- Interpreter invocation
g++ -std=c++17 -Wall -Wextra -Werror snippet.cpp -pthread -lm -o snippet && ./snippet- Container image ID
sha256:32dc2d998158b6554c99b73b533f423696a0f3e31e8cbea9db10b5eee9a2fadd- Code SHA-256
ba4fae2311152572b432955a57c077b96689882c5c87060393645a5ea97c66ee- Dependencies
- g++ 4:13.2.0-7ubuntu1
Test input setup
These are the prepared inputs used by the test harness. See Details above for the prerequisites and how to run this example.
# No input files required.
Observed standard output
5
Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.