+ Coerce() skeleton

Author: romainfrancois

r/src/altrep.cpp

@@ -280,6 +280,11 @@ struct AltrepArrayPrimitive {
   }
 
   static SEXP Unserialize(SEXP /* class_ */, SEXP state) { return state; }
+
+  SEXP Coerce(int type) {
+    // Just let R handle it for now
+    return NULL;
+  }
 };
 template <int sexp_type>
 R_altrep_class_t AltrepArrayPrimitive<sexp_type>::class_t;
@@ -344,6 +349,11 @@ SEXP Unserialize(SEXP class_, SEXP state) {
   return AltrepClass::Unserialize(class_, state);
 }
 
+template <typename AltrepClass>
+SEXP Coerce(SEXP alt, int type) {
+  return AltrepClass(alt).Coerce(type);
+}
+
 static std::shared_ptr<arrow::compute::ScalarAggregateOptions> NaRmOptions(
     const std::shared_ptr<Array>& array, bool na_rm) {
   auto options = std::make_shared<arrow::compute::ScalarAggregateOptions>(
@@ -435,6 +445,7 @@ void InitAltrepMethods(R_altrep_class_t class_t, DllInfo* dll) {
   R_set_altrep_Duplicate_method(class_t, Duplicate<AltrepClass>);
   R_set_altrep_Serialized_state_method(class_t, Serialized_state<AltrepClass>);
   R_set_altrep_Unserialize_method(class_t, Unserialize<AltrepClass>);
+  R_set_altrep_Coerce_method(class_t, Coerce<AltrepClass>);
 }
 
 template <typename AltrepClass>

r/tests/testthat/test-altrep.R

@@ -192,9 +192,16 @@ test_that("altrep min/max/sum identical to R versions for int", {
 
 test_that("altrep vectors handle serialization", {
   ints <- c(1L, 2L, NA_integer_)
-  dbls <- c(3, 4, NA_real_)
+  dbls <- c(1, 2, NA_real_)
 
   expect_identical(ints, unserialize(serialize(Array$create(ints)$as_vector(), NULL)))
   expect_identical(dbls, unserialize(serialize(Array$create(dbls)$as_vector(), NULL)))
 })
 
+test_that("altrep vectors handle coercion", {
+  ints <- c(1L, 2L, NA_integer_)
+  dbls <- c(1, 2, NA_real_)
+
+  expect_identical(ints, as.integer(Array$create(dbls)$as_vector()))
+  expect_identical(dbls, as.numeric(Array$create(ints)$as_vector()))
+})