/in/foo.cc: In function 'int main()':
/in/foo.cc:8:11: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
  if(ch='+')
           ^
/in/foo.cc:10:11: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
  if(ch='-')
           ^