W:=f(g(x))   
   Means in expression W I can identify   
   a sub expression g(x) that depends of x and in W there is no other   
   subexpression that depends from x   
      
   Int(f(g(x)), x)==   
   If isCostant(k:=D(g(x),x)) and   
      (F:=Int(f(y)/k,y)).error!="fail"   
        return subst(F,y=g(x))   
   else r:=Int(f(g(x)), x)   
        r.error:="fail"   
        return r   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)