View Compilation Error

0_0_19979720_24434.cpp: In function 'void query(int, int, int, int, int)':
0_0_19979720_24434.cpp:58:18: error: 'ans' was not declared in this scope
   if(x>=l&&r<=y) ans=merge(ans,t[p]);
                  ^
0_0_19979720_24434.cpp:66:33: error: conversion from 'void' to non-scalar type 'node' requested
       node a=query(p*2,l,mid,x,y);
                                 ^
0_0_19979720_24434.cpp:67:37: error: conversion from 'void' to non-scalar type 'node' requested
       node b=query(p*2+1,mid+1,r,x,y);
                                     ^
0_0_19979720_24434.cpp:68:7: error: 'ans' was not declared in this scope
       ans=merge(ans,merge(a,b));
       ^