feat(furvm): implement constants

Closes: #13

furvm/include/furvm/constant.hpp

@@ -1,74 +1,29 @@
 #ifndef FURVM_CONSTANT_HPP
 #define FURVM_CONSTANT_HPP
 
-#include "furvm/exceptions.hpp"
 #include "furvm/fwd.hpp"
 
+#include <cstdint>
 #include <string_view>
 
 namespace furvm {
 
-enum class constant_t : std::uint8_t {
-    String, /**< String constant. */
-};
-
-class constant {
-public:
-    using string_type = std::string_view; /**< String constant type. */
-public:
-    /**
-     * @brief Construct a new string constant.
-     *
-     * @param string String.
-     */
-    constant(string_type string)
-      : m_type(constant_t::String), m_value(string) {}
-
-    ~constant() = default;
-
-    /**
-     * @brief Move constructor.
-     */
-    constant(constant&&) = default;
-
-    /**
-     * @brief Move constructor.
-     */
-    constant& operator=(constant&&) = default;
-
-    constant(const constant&)            = delete;
-    constant& operator=(const constant&) = delete;
-public:
-    /**
-     * @brief Returns this constant's type.
-     * @see constant_t
-     *
-     * @return The constant type.
-     */
-    constexpr constant_t type() const { return m_type; }
-
-    /**
-     * @brief Returns this constant's string value.
-     * @throws bad_constant_access if this constant's type is not constant_t::String.
-     *
-     * @return The string value.
-     */
-    constexpr string_type string() const {
-        require_type(constant_t::String);
-        return m_value.string;
-    }
-private:
-    void require_type(constant_t type) const {
-        if (m_type != type) throw bad_constant_access();
-    }
-private:
-    constant_t m_type{};
-    union value {
-        string_type string;
-
-        value(string_type sv)
-          : string(sv) {}
-    } m_value;
+// TODO: Array constants
+struct constant {
+    enum type_e {
+        S32 = 0,
+        U32,
+        S64,
+        U64,
+        String,
+    } type = S32;
+    union {
+        std::int32_t     s32;
+        std::uint32_t    u32;
+        std::int64_t     s64;
+        std::uint64_t    u64;
+        std::string_view string;
+    };
 };
 
 } // namespace furvm

furvm/include/furvm/module.hpp

@@ -3,6 +3,7 @@
 
 #include "furlang/utility/hash.hpp"
 #include "furlang/view.hpp"
+#include "furvm/constant.hpp"
 #include "furvm/function.hpp"
 #include "furvm/fwd.hpp"
 #include "furvm/handle.hpp"
@@ -10,8 +11,6 @@
 
 #include <functional>
 #include <istream>
-#include <limits>
-#include <optional>
 #include <ostream>
 #include <stdexcept>
 #include <string>
@@ -384,6 +383,13 @@ public:
         if (var >= m_globalVariables.size()) throw std::runtime_error("invalid slot");
         return m_globalVariables[var];
     }
+public:
+    template <typename... Args, typename = std::enable_if_t<std::is_constructible_v<constant, Args...>>>
+    void emplace_constant(Args&&... args) {
+        m_constants.emplace_back(std::forward<Args>(args)...);
+    }
+
+    const constant& constant_at(constant_index index) const { return m_constants.at(index); }
 public:
     template <typename Fwd, typename = std::enable_if_t<std::is_constructible_v<breakpoint, Fwd>>>
     void set_breakpoint(bytecode_pos pos, Fwd&& breakpoint) {
@@ -423,6 +429,8 @@ private:
 
     std::vector<thing<>> m_globalVariables;
 
+    std::vector<constant> m_constants;
+
     std::unordered_map<std::string, native_function> m_nativeFunctions;
 
     std::unordered_map<bytecode_pos, breakpoint> m_breakpoints;