/in/p2.cpp: In function 'bool tree_search(tree_t, int)':
/in/p2.cpp:104:26: warning: suggest parentheses around comparison in operand of '|' [-Wparentheses]
     return tree_elt(tree)==val|tree_search(tree_left(tree),val)|tree_search(tree_right(tree),val);
            ~~~~~~~~~~~~~~^~~~~
/in/p2.cpp: In function 'opaque_list* traversal(tree_t)':
/in/p2.cpp:123:1: warning: no return statement in function returning non-void [-Wreturn-type]
 }
 ^
/tmp/cc6u6Cru.o: In function `main':
main.cpp:(.text+0x6c4): undefined reference to `tree_hasMonotonicPath(opaque_tree*)'
main.cpp:(.text+0x728): undefined reference to `tree_allPathSumGreater(opaque_tree*, int)'
main.cpp:(.text+0x78c): undefined reference to `tree_allPathSumGreater(opaque_tree*, int)'
main.cpp:(.text+0x7f2): undefined reference to `covered_by(opaque_tree*, opaque_tree*)'
main.cpp:(.text+0x858): undefined reference to `contained_by(opaque_tree*, opaque_tree*)'
main.cpp:(.text+0x8bc): undefined reference to `insert_tree(int, opaque_tree*)'
collect2: error: ld returned 1 exit status