/in/foo.c: In function 'main':
/in/foo.c:12:2: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
  if(delter=0)
  ^~
/in/foo.c:27:12: error: 'delta' undeclared (first use in this function)
    s=sqrt(-delta)/(2*a);
            ^~~~~
/in/foo.c:27:12: note: each undeclared identifier is reported only once for each function it appears in