couple of fixes suggested by Claude

Author: Enchufa2

ChangeLog

@@ -6,10 +6,12 @@
 
 	* inst/include/Rcpp/sugar/functions/cumprod.h: Use the previous operations
 	* inst/include/Rcpp/sugar/functions/cumsum.h: Idem
-	* inst/include/Rcpp/sugar/functions/diff.h: Idem
+	* inst/include/Rcpp/sugar/functions/diff.h: Idem, also fixed a bug where
+	the diff was recomputed instead of returning the calculated value
 	* inst/include/Rcpp/sugar/functions/rowSums.h: Idem
 	* inst/include/Rcpp/sugar/functions/sum.h: Idem
-	* inst/include/Rcpp/sugar/operators/minus.h: Idem
+	* inst/include/Rcpp/sugar/operators/minus.h: Idem, also fixed a bug for
+	an incorrect Extractor specialization in Minus_Primitive_Vector
 	* inst/include/Rcpp/sugar/operators/plus.h: Idem
 	* inst/include/Rcpp/sugar/operators/times.h: Idem
 

inst/include/Rcpp/sugar/functions/diff.h

@@ -106,10 +106,10 @@ class Diff<RTYPE,false,LHS_T> : public Rcpp::VectorBase< RTYPE, false , Diff<RTY
 	inline STORAGE operator[]( R_xlen_t i ) const {
 		STORAGE y = lhs[i+1] ;
 		if( previous_index != i ) previous = lhs[i] ;
-		STORAGE diff = RCPP_SAFE_SUB(y, previous);
+		STORAGE res = RCPP_SAFE_SUB(y, previous);
 		previous = y ;
 		previous_index = i+1 ;
-		return RCPP_SAFE_SUB(y, previous);
+		return res;
 	}
 	inline R_xlen_t size() const { return lhs.size() - 1 ; }