I not have any practice on CAS sys   
   for doing rules(macro substitution conditional on type and set I suppose)   
   but if a can imagine a sys and a law   
   for Int(f(g(x)),x)   
   [as example Int(f(2*x+1),x)]   
    it will do the same thing I would write in a paper and pencil:   
      
   Int(f(g(x)), x)==   
   If isCostant(k:=D(g(x),x)) and   
      (F:=Int(f(y)/k,y))!="fail"   
     return subst(F,y=g(x))   
   else return Int(f(g(x)), x)   
      
   How to identify f and g in one expression I don't know   
      
   Possibly I make some error...   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)