route range-to-range assignment through the aliasing checks

Also mark Range as elementwise, include sugar_operand.h from
is_elementwise.h, and drop stale FIXME comments in ifelse.h.

Author: kevinushey

inst/include/Rcpp/sugar/Range.h

@@ -27,6 +27,8 @@ namespace Rcpp{
 
     class Range : public VectorBase<INTSXP,false, Range >{
     public:
+        typedef traits::elementwise_operands<> rcpp_elementwise ;
+
         Range( R_xlen_t start_, R_xlen_t end__ ) : start(start_), end_(end__){
             if( start_ > end__ ){
                 throw std::range_error( "upper value must be greater than lower value" ) ;

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

@@ -287,9 +287,7 @@ class IfElse_Primitive_Primitive : public VectorBase<
 	typedef Rcpp::traits::elementwise_operands< COND_TYPE > rcpp_elementwise ;
 
 	IfElse_Primitive_Primitive( const COND_TYPE& cond_, STORAGE lhs_, STORAGE rhs_ ) :
-		cond(cond_.get_ref()), lhs(lhs_), rhs(rhs_)  {
-			/* FIXME : cond, lhs and rhs must all have the same size */
-	}
+		cond(cond_.get_ref()), lhs(lhs_), rhs(rhs_) {}
 
 	inline STORAGE operator[]( R_xlen_t i ) const {
 		int x = cond[i] ;
@@ -321,9 +319,7 @@ class IfElse_Primitive_Primitive<RTYPE,false,COND_T> : public VectorBase<
 	typedef Rcpp::traits::elementwise_operands< COND_TYPE > rcpp_elementwise ;
 
 	IfElse_Primitive_Primitive( const COND_TYPE& cond_, STORAGE lhs_, STORAGE rhs_ ) :
-		cond(cond_.get_ref()), lhs(lhs_), rhs(rhs_) {
-			/* FIXME : cond, lhs and rhs must all have the same size */
-	}
+		cond(cond_.get_ref()), lhs(lhs_), rhs(rhs_) {}
 
 	inline STORAGE operator[]( R_xlen_t i ) const {
 		return cond[i] ? lhs : rhs ;

inst/include/Rcpp/traits/is_elementwise.h

@@ -23,6 +23,8 @@
 #ifndef Rcpp__traits__is_elementwise_h
 #define Rcpp__traits__is_elementwise_h
 
+#include <Rcpp/traits/sugar_operand.h>
+
 namespace Rcpp{
 namespace traits{
 

inst/include/Rcpp/vector/RangeIndexer.h

@@ -67,11 +67,20 @@ class RangeIndexer : public VectorBase<RTYPE, NA, RangeIndexer<RTYPE,NA,VECTOR>
 	RangeIndexer( VECTOR& vec_, const Rcpp::Range& range_) :
 		start(vec_.begin() + range_.get_start() ), size_( range_.size() ) {}
 
+	RangeIndexer( const RangeIndexer& other ) :
+		start(other.start), size_(other.size_) {}
+
 	template <bool NA_, typename T>
 	RangeIndexer& operator=( const Rcpp::VectorBase<RTYPE,NA_,T>& x){
 	    UNROLL_LOOP(=)
 	}
 
+	// without this, assigning one range to another would use the implicit
+	// copy assignment, which rebinds this range instead of copying elements
+	RangeIndexer& operator=( const RangeIndexer& x ){
+	    return operator=( static_cast<const Rcpp::VectorBase<RTYPE,NA,RangeIndexer>&>(x) ) ;
+	}
+
 	template <bool NA_, typename T>
 	RangeIndexer& operator+=( const Rcpp::VectorBase<RTYPE,NA_,T>& x){
 		 UNROLL_LOOP(+=)

inst/tinytest/cpp/sugar_expressions.cpp

@@ -149,6 +149,20 @@ NumericVector alias_range_shift(NumericVector x) {
     return x;
 }
 
+// [[Rcpp::export]]
+NumericVector alias_range_range(NumericVector x) {
+    R_xlen_t n = x.size();
+    x[Range(1, n - 1)] = x[Range(0, n - 2)];
+    return x;
+}
+
+// [[Rcpp::export]]
+NumericVector alias_range_range_add(NumericVector x) {
+    R_xlen_t n = x.size();
+    x[Range(1, n - 1)] += x[Range(0, n - 2)];
+    return x;
+}
+
 // [[Rcpp::export]]
 NumericVector alias_range_rev(NumericVector x) {
     R_xlen_t n = x.size();
@@ -223,6 +237,7 @@ LogicalVector elementwise_flags(NumericVector x, NumericMatrix m) {
     bool row_row         = traits::is_elementwise<decltype(m(0, _) + 1.0), RT>::value;
     bool row_column      = traits::is_elementwise<decltype(m(0, _) + 1.0), CT>::value;
     bool range_range     = traits::is_elementwise<decltype(x[Range(0, 1)] + 1.0), GT>::value;
+    bool sequence        = traits::is_elementwise<decltype(seq(0, 1)), GT>::value;
 
     return LogicalVector::create(
         _["vector"]        = vector,
@@ -237,7 +252,8 @@ LogicalVector elementwise_flags(NumericVector x, NumericMatrix m) {
         _["column_row"]    = column_row,
         _["row_row"]       = row_row,
         _["row_column"]    = row_column,
-        _["range_range"]   = range_range
+        _["range_range"]   = range_range,
+        _["seq"]           = sequence
     );
 }
 
@@ -277,6 +293,12 @@ NumericVector length_range(NumericVector x, NumericVector y) {
     return x;
 }
 
+// [[Rcpp::export]]
+NumericVector length_range_range(NumericVector x) {
+    x[Range(0, 1)] = x[Range(0, 3)];
+    return x;
+}
+
 // [[Rcpp::export]]
 NumericMatrix length_column(NumericMatrix m, NumericVector y) {
     m(_, 0) = y;

inst/tinytest/test_sugar.R

@@ -1734,6 +1734,8 @@ expect_equal(alias_mixed(x()), x() + rev(x()), info = "x = x + rev(x)")
 expect_equal(alias_sapply(x()), x() - x()[1], info = "x = sapply(x, <reads x[0]>)")
 expect_equal(alias_elementwise(x()), x() * 2 + x(), info = "x = x * 2 + x")
 expect_equal(alias_range_shift(x()), c(1, 1, 2, 3, 4), info = "x[1:n-1] = head(x, n-1)")
+expect_equal(alias_range_range(x()), c(1, 1, 2, 3, 4), info = "x[1:n-1] = x[0:n-2]")
+expect_equal(alias_range_range_add(x()), c(1, 3, 5, 7, 9), info = "x[1:n-1] += x[0:n-2]")
 expect_equal(alias_range_rev(x()), rev(x()), info = "x[0:n-1] = rev(x)")
 expect_equal(alias_range_add_rev(x()), x() + rev(x()), info = "x[0:n-1] += rev(x)")
 m <- function() matrix(c(1, 2, 3, 4, 5, 6), 3)
@@ -1761,7 +1763,7 @@ expect_equal(
     c(vector = TRUE, arith = TRUE, math = TRUE, ifelse = TRUE,
       rev = FALSE, arith_rev = FALSE, head = FALSE,
       column_vector = TRUE, column_column = TRUE, column_row = FALSE,
-      row_row = TRUE, row_column = FALSE, range_range = FALSE),
+      row_row = TRUE, row_column = FALSE, range_range = FALSE, seq = TRUE),
     info = "traits::is_elementwise"
 )
 
@@ -1780,6 +1782,7 @@ expect_error(length_ifelse(c(TRUE, FALSE), c(1, 2), c(1, 2, 3)), "different leng
 expect_equal(length_range(c(1, 2, 3, 4, 5), c(7, 8, 9)), c(7, 8, 9, 4, 5), info = "x[0:2] = y")
 expect_error(length_range(c(1, 2, 3, 4, 5), c(7, 8)), "cannot assign", info = "x[0:2] = <shorter y>")
 expect_error(length_range(c(1, 2, 3, 4, 5), c(6, 7, 8, 9)), "cannot assign", info = "x[0:2] = <longer y>")
+expect_error(length_range_range(c(1, 2, 3, 4, 5)), "cannot assign", info = "x[0:1] = x[0:3]")
 expect_error(length_column(matrix(1, 3, 2), c(7, 8)), "cannot assign", info = "m(_, 0) = <shorter y>")
 expect_error(length_row(matrix(1, 3, 2), c(7, 8, 9)), "cannot assign", info = "m(0, _) = <longer y>")