1 files changed, 117 insertions, 0 deletions
diff --git a/cpp/021address b/cpp/021address
new file mode 100644
index 00000000..22355fc6
--- /dev/null
+++ b/cpp/021address
@@ -0,0 +1,117 @@
+//: Instructions can read from addresses pointing at other locations using the
+//: 'deref' property.
+:(scenario "copy_indirect")
+recipe main [
+  1:address:integer <- copy 2:literal
+  2:integer <- copy 34:literal
+  # This loads location 1 as an address and looks up *that* location.
+  3:integer <- copy 1:address:integer/deref
+]
++run: instruction main/2
++mem: location 1 is 2
++mem: location 2 is 34
++mem: storing 34 in location 3
+
+:(before "int base = x.value" following "vector<int> read_memory(reagent x)")
+x = canonize(x);
+
+//: similarly, write to addresses pointing at other locations using the
+//: 'deref' property
+:(scenario "store_indirect")
+recipe main [
+  1:address:integer <- copy 2:literal
+  1:address:integer/deref <- copy 34:literal
+]
++run: instruction main/1
++mem: location 1 is 2
++mem: storing 34 in location 2
+
+:(before "int base = x.value" following "void write_memory(reagent x, vector<int> data)")
+x = canonize(x);
+
+:(code)
+reagent canonize(reagent x) {
+//?   cout << "canonize\n"; //? 1
+  reagent r = x;
+//?   cout << x.to_string() << " => " << r.to_string() << '\n'; //? 1
+  while (has_property(r, "deref"))
+    r = deref(r);
+  return r;
+}
+
+bool has_property(reagent x, string name) {
+  for (size_t i = 0; i < x.properties.size(); ++i) {
+    if (x.properties[i].first == name) return true;
+  }
+  return false;
+}
+
+reagent deref(reagent x) {
+//?   cout << "deref: " << x.to_string() << "\n"; //? 2
+  static const int ADDRESS = Type_number["address"];
+  reagent result;
+  assert(x.types[0] == ADDRESS);
+
+  // compute value
+  result.set_value(Memory[x.value]);
+  trace("mem") << "location " << x.value << " is " << result.value;
+
+  // populate types
+  copy(++x.types.begin(), x.types.end(), inserter(result.types, result.types.begin()));
+
+  // drop-one 'deref'
+  int i = 0;
+  int len = x.properties.size();
+  for (i = 0; i < len; ++i) {
+    if (x.properties[i].first == "deref") break;
+    result.properties.push_back(x.properties[i]);
+  }
+  ++i;  // skip first deref
+  for (; i < len; ++i) {
+    result.properties.push_back(x.properties[i]);
+  }
+  return result;
+}
+
+//: 'get' can read from container address
+:(scenario "get_indirect")
+recipe main [
+  1:integer <- copy 2:literal
+  2:integer <- copy 34:literal
+  3:integer <- copy 35:literal
+  4:integer <- get 1:address:point/deref, 0:offset
+]
++run: instruction main/3
++run: address to copy is 2
++run: product 0 is 34
++mem: storing 34 in location 4
+
+:(scenario "include_nonderef_properties")
+recipe main [
+  1:integer <- copy 2:literal
+  2:integer <- copy 34:literal
+  3:integer <- copy 35:literal
+  4:integer <- get 1:address:point/deref/foo, 0:offset
+]
++run: instruction main/3
++run: address to copy is 2
++run: product 0 is 34
++mem: storing 34 in location 4
+
+:(after "reagent base = " following "case GET:")
+base = canonize(base);
+
+:(scenario "get_address_indirect")
+# 'get' can read from container address
+recipe main [
+  1:integer <- copy 2:literal
+  2:integer <- copy 34:literal
+  3:integer <- copy 35:literal
+  4:integer <- get-address 1:address:point/deref, 0:offset
+]
++run: instruction main/3
++run: address to copy is 2
++run: product 0 is 2
+
+:(after "reagent base = " following "case GET_ADDRESS:")
+base = canonize(base);