main.c: In function ‘main’:
main.c:38:50: error: expected ‘}’ before ‘else’
  FOR(i) if(fabs(cs[i]) < cmax*filter) { ca[i]=0; else ca[i]=cs[i];}
                                                  ^~~~
main.c:37:10: warning: variable ‘ca’ set but not used [-Wunused-but-set-variable]
  complex ca[N];
          ^~
main.c:39:13: error: ‘N’ undeclared (first use in this function)
  complex ys[N];
             ^
main.c:39:13: note: each undeclared identifier is reported only once for each function it appears in
main.c:40:8: error: ‘ca’ undeclared (first use in this function)
  ift(N,ca,ys);
        ^~
In file included from main.c:2:
main.c:41:32: error: ‘ts’ undeclared (first use in this function); did you mean ‘ys’?
  FOR(i) printf("%g %g\n",creal(ts[i]),creal(ys[i]));
                                ^~
main.c:41:26: error: invalid type of argument 1 of type-generic function
  FOR(i) printf("%g %g\n",creal(ts[i]),creal(ys[i]));
                          ^~~~~
main.c:41:39: error: invalid type of argument 1 of type-generic function
  FOR(i) printf("%g %g\n",creal(ts[i]),creal(ys[i]));
                                       ^~~~~
main.c:39:10: warning: unused variable ‘ys’ [-Wunused-variable]
  complex ys[N];
          ^~
main.c: At top level:
main.c:43:1: error: expected identifier or ‘(’ before ‘}’ token
 }
 ^
make: *** [<builtin>: main.o] Error 1