Compute FIRST sets correctly

spec/compiler/build_tables/next_symbols_spec.cpp

@@ -0,0 +1,38 @@
+#include "spec_helper.h"
+#include "build_tables/next_symbols.h"
+#include "grammar.h"
+#include "rules.h"
+
+using std::set;
+using namespace build_tables;
+using namespace rules;
+
+START_TEST
+
+describe("computing FIRST sets", []() {
+    Grammar grammar({
+        { "A", choice({
+            seq({
+                sym("B"),
+                sym("x"),
+                sym("B") }),
+            sym("B") }) },
+        { "B", choice({
+            seq({
+                sym("y"),
+                sym("z"),
+                sym("y") }),
+            sym("y") }) },
+    });
+    
+    describe("for a rule", [&]() {
+        it("searches the tree for terminals", [&]() {
+            auto terminals = next_terminals(grammar.rules.find("A")->second, grammar);
+            AssertThat(terminals, Equals(set<Symbol>({
+                Symbol("y")
+            })));
+        });
+    });
+});
+
+END_TEST

spec/spec_helper.h

@@ -4,6 +4,7 @@
 #include "bandit/bandit.h"
 #include <iostream>
 #include <unordered_set>
+#include <set>
 #include <unordered_map>
 #include "grammar.h"
 
@@ -26,7 +27,19 @@ namespace std {
         }
         return stream << ">";
     }
-    
+
+    template<typename T>
+    inline ostream& operator<<(ostream &stream, const set<T> &set) {
+        stream << string("#<set: ");
+        bool started = false;
+        for (auto item : set) {
+            if (started) stream << string(", ");
+            stream << item;
+            started = true;
+        }
+        return stream << ">";
+    }
+
     template<typename TKey, typename TValue>
     inline ostream& operator<<(ostream &stream, const unordered_map<TKey, TValue> &map) {
         stream << string("#<map: ");