GraphNodeData

    
        GraphNodeForeachPredecessor(GraphGetNode(&graph, d), predecessor) {
            predecessor_sum += GraphNodeData(&graph, predecessor);
            predecessor_count += 1;
        }

    
        GraphForeachNode(&graph, node) {
            if (GraphNodeData(&graph, node) == 20) {
                GraphMarkNodeForDeletion(node);
            }

        result = result && (GraphNodeIdIndex(d) == GraphNodeIdIndex(b));
        result = result && (GraphNodeIdGeneration(d) == (GraphNodeIdGeneration(b) + 1));
        result = result && (GraphNodeData(&graph, GraphGetNode(&graph, d)) == 40);
        result = result && !GraphNodeVisited(GraphGetNode(&graph, d));

        result      = result && GraphContainsNode(&graph, a) && GraphContainsNode(&graph, b) && GraphContainsNode(&graph, c);
        result      = result && GraphNodeAt(&graph, b) == 25;
        result      = result && GraphNodeData(&graph, node_b) == 25;
        result      = result && GraphNodeGetId(node_b) == b;
        result      = result && GraphNodeIndex(node_b) == GraphNodeIdIndex(b);

    
    static bool test_graph_cross_graph_node_handle_deadend(void) {
        WriteFmt("Testing GraphNodeData rejects foreign graph node handles (should abort)\n");
    
        typedef Graph(int) IntGraph;

        GraphNode node   = GraphGetNode(&graph_a, GraphAddNodeR(&graph_a, 10));
    
        (void)GraphNodeData(&graph_b, node);
    
        GraphDeinit(&graph_b);