Begin working on let statements

Author: toroidal-code

include/cppspec.hpp

@@ -14,6 +14,9 @@
 #define before_each self.before_each
 #define after_all self.after_all
 #define after_each self.after_each
+#define let(name, body)              \
+  auto name = make_let(#name, body); \
+  self.let(#name, name)
 
 typedef Description describe;
 

include/description.hpp

@@ -3,13 +3,14 @@
 
 #include <string>
 #include <queue>
-#include <map>
+#include <unordered_map>
 #include <functional>
 #include <iostream>
 #include <memory>
 #include "util.hpp"
 #include "runnable.hpp"
 #include "it.hpp"
+#include "let.hpp"
 
 template <class T>
 class ClassDescription;
@@ -24,6 +25,7 @@ class Description : public Runnable {
   std::deque<rule_block_t> after_alls;
   std::deque<rule_block_t> before_eaches;
   std::deque<rule_block_t> after_eaches;
+  std::unordered_map<std::string, Runnable *> lets;
 
   explicit Description(std::string descr) : descr(descr){};
 
@@ -64,6 +66,8 @@ class Description : public Runnable {
   void exec_before_eaches();
   void exec_after_eaches();
 
+  void let(std::string name, Runnable &body);
+
   bool run();
 };
 
@@ -144,6 +148,11 @@ void Description::exec_after_eaches() {
   for (rule_block_t b : after_eaches) b();
 }
 
+void Description::let(std::string name, Runnable &body) {
+  auto p = lets.insert({name, &body});
+  if (!p.second) p.first->second = &body;  // assign if the key is already there
+}
+
 bool Description::run() {
   std::cout << padding() << descr << std::endl;
   body(*this);

include/let.hpp

@@ -0,0 +1,38 @@
+#ifndef LET_H
+#define LET_H
+#include <functional>
+#include <type_traits>
+#include <iostream>
+#include "runnable.hpp"
+
+template <typename T>
+class Let : public Runnable {
+  typedef std::function<T()> block_t;
+
+  std::string name;
+  block_t body;
+
+ public:
+  explicit Let(std::string name, block_t body) : name(name), body(body){};
+  bool run();
+};
+
+template <typename T>
+bool Let<T>::run() {
+  body();
+  return true;
+}
+
+/**
+ * @brief Object generator for Let.
+ *
+ * @param body the body of the let statement
+ *
+ * @return a new Let object
+ */
+template <typename T>
+auto make_let(std::string name, T body) -> Let<decltype(body())> {
+  return Let<decltype(body())>(name, body);
+}
+
+#endif /* LET_H */