Function intern_set

docs/app/js/sanddance-app.js:110726–110731

({ _intern , _key  }, value)

    return _intern.has(key) ? _intern.get(key) : value;
}
function intern_set({ _intern , _key  }, value) {
    const key = _key(value);
    if (_intern.has(key)) return _intern.get(key);
    _intern.set(key, value);
    return value;
}
function intern_delete({ _intern , _key  }, value) {
    const key = _key(value);
    if (_intern.has(key)) {