/in/foo.c: In function 'main':
/in/foo.c:6:1: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
 while(xmin=1<1000)
 ^~~~~
/in/foo.c:13:9: error: 'x1' undeclared (first use in this function)
   while(x1<x)
         ^~
/in/foo.c:13:9: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:25:1: error: expected declaration or statement at end of input
 }
 ^