View Compilation Error

0_0_23798595_13104.cpp:6:12: error: expected unqualified-id before ')' token
 struct fun(){
            ^
0_0_23798595_13104.cpp:9:2: error: 'f' does not name a type
 }f[105];
  ^
0_0_23798595_13104.cpp: In function 'bool cmp(fun, fun)':
0_0_23798595_13104.cpp:10:14: error: 'a' has incomplete type
 bool cmp(fun a,fun b){
              ^
0_0_23798595_13104.cpp:6:8: error: forward declaration of 'struct fun'
 struct fun(){
        ^
0_0_23798595_13104.cpp:10:20: error: 'b' has incomplete type
 bool cmp(fun a,fun b){
                    ^
0_0_23798595_13104.cpp:6:8: error: forward declaration of 'struct fun'
 struct fun(){
        ^
0_0_23798595_13104.cpp: In function 'int main()':
0_0_23798595_13104.cpp:20:29: error: 'f' was not declared in this scope
             scanf("%d %lf",&f[i].x,&f[i].y);
                             ^
0_0_23798595_13104.cpp:21:14: error: 'f' was not declared in this scope
         sort(f,f+b,cmp);
              ^
0_0_23798595_13104.cpp:38:29: error: 'mesmet' was not declared in this scope
         mesmet(f,0,sizeof(f));
                             ^