View Compilation Error

0_0_24474499_8688.cpp: In function 'vi next()':
0_0_24474499_8688.cpp:34:13: error: 'expr' was not declared in this scope
 vi v = expr(); p ++;
             ^
0_0_24474499_8688.cpp:43:11: error: a function-definition is not allowed here before '{' token
 vi expr() {
           ^
0_0_24474499_8688.cpp:87:1: error: expected '}' at end of input
 }
 ^