diff --git a/eqpalg/utility/expression_engine.cpp b/eqpalg/utility/expression_engine.cpp
new file mode 100644
index 0000000..0260c29
--- /dev/null
+++ b/eqpalg/utility/expression_engine.cpp
@@ -0,0 +1,72 @@
+// eqpalg/utility/expression_engine.cpp
+#include <eqpalg/utility/expression_engine.h>
+#include <glob/SingletonTemplate.h>
+#include <eqpalg/gb_item_memory.h>
+#include <mix_cc/type/mix_time.h>
+#include <log4cplus/LOG.h>
+
+ExpressionEngine::ExpressionEngine(std::map<std::string, double>& mm_vars,
+                                   std::vector<std::string>& m_tags)
+    : mm_vars_(mm_vars), m_tags_(m_tags) {}
+
+// 惰性初始化 VarsCache（首次变量刷新时调用）
+static void ensureVarCache(VarsCache& vc, size_t tag_count) {
+  if (vc.tag_num == 0 && tag_count > 0) {
+    vc.init(tag_count, 6);
+  }
+}
+
+int ExpressionEngine::registerExpression(const std::string& name,
+                                          const std::string& raw_exp_str) {
+  if (exps_.count(name)) return 0;  // 已注册，幂等
+
+  auto& entry = exps_[name];
+  entry.raw_str = raw_exp_str;
+
+  // 通过 FunVars 替换状态函数（KeepC/KeepT/RiseEdge/Detect）为 funN 变量
+  auto [ok, processed] = fun_vars_.add_exp_str(raw_exp_str, &mm_vars_);
+  if (!ok) return -1;
+  entry.processed_str = processed;
+
+  // 编译表达式
+  try {
+    entry.ptr = std::make_unique<MExp>(processed, &mm_vars_);
+  } catch (const std::exception& e) {
+    return -1;
+  }
+
+  // 从表达式中提取 hold(n,T) 模式
+  initHoldExpStr(processed);
+
+  return 0;
+}
+
+int ExpressionEngine::registerRawExpression(const std::string& name,
+                                             const std::string& raw_exp_str) {
+  if (exps_.count(name)) return 0;
+
+  auto& entry = exps_[name];
+  entry.raw_str = raw_exp_str;
+  entry.processed_str = raw_exp_str;
+
+  try {
+    entry.ptr = std::make_unique<MExp>(raw_exp_str, &mm_vars_);
+  } catch (const std::exception& e) {
+    return -1;
+  }
+  return 0;
+}
+
+double ExpressionEngine::evaluate(const std::string& name) {
+  auto it = exps_.find(name);
+  if (it == exps_.end()) return 0.0;
+  return it->second.ptr->evaluate();
+}
+
+bool ExpressionEngine::evaluateBool(const std::string& name) {
+  return static_cast<bool>(evaluate(name));
+}
+
+int ExpressionEngine::initHoldExpStr(const std::string& exp_str) {
+  return 0;  // stub — Task 5 will implement
+}