19

intcode/include/intcode/Machine.hpp

@@ -27,6 +27,7 @@ public:
   /// @param address
   /// @return reference to memory at given address
   auto At(std::size_t address) -> ValueType &;
+  auto At(std::size_t address) const -> ValueType;
 
   /// Access memory at address relative to base pointer
   /// @param offset from base pointer

intcode/src/Machine.cpp

@@ -11,6 +11,12 @@ auto Machine::At(std::size_t const i) -> ValueType & {
   return i < rom_.size() ? rom_[i] : ram_[i];
 }
 
+auto Machine::At(std::size_t const i) const -> ValueType {
+  if (i < rom_.size()) return rom_[i];
+  if (auto it = ram_.find(i); it != ram_.end()) { return it->second; }
+  return 0;
+}
+
 auto Machine::Rel(std::size_t const i) -> ValueType & {
   return At(base_ + i);
 }