xiiregexbuilder

commit f49928c22a00c08d06453648856f90d4d2abf537
parent 6f7343019c63029335be0494abf485190a017509
Author: Achuthan TM <achuthantm05@gmail.com>
Date:   Sun, 29 Mar 2026 07:13:50 +0530

Week 2: Implement Glushkov NFA Builder (Part 3: Finalizing)

Diffstat:
M
src/nfa.cpp
 | 
61
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
M
src/nfa.h
 | 
11
+++++++++++

2 files changed, 72 insertions(+), 0 deletions(-)
diff --git a/src/nfa.cpp b/src/nfa.cpp
@@ -204,3 +204,64 @@ void NFABuilder::computeNullableFirstLast(ASTNode* node) {
             n->lastpos = n->inner->lastpos;
             break;
         }
+        case ASTNodeType::PLUS: {
+            auto n = static_cast<PlusNode*>(node);
+            computeNullableFirstLast(n->inner.get());
+            n->nullable = n->inner->nullable;
+            n->firstpos = n->inner->firstpos;
+            n->lastpos = n->inner->lastpos;
+            break;
+        }
+        case ASTNodeType::OPTIONAL: {
+            auto n = static_cast<OptionalNode*>(node);
+            computeNullableFirstLast(n->inner.get());
+            n->nullable = true;
+            n->firstpos = n->inner->firstpos;
+            n->lastpos = n->inner->lastpos;
+            break;
+        }
+    }
+}
+
+void NFABuilder::computeFollowpos(ASTNode* node, std::map<int, std::set<int>>& followpos) {
+    if (!node) return;
+    switch (node->type) {
+        case ASTNodeType::CONCATENATION: {
+            auto n = static_cast<ConcatenationNode*>(node);
+            computeFollowpos(n->left.get(), followpos);
+            computeFollowpos(n->right.get(), followpos);
+            for (int p : n->left->lastpos) {
+                followpos[p].insert(n->right->firstpos.begin(), n->right->firstpos.end());
+            }
+            break;
+        }
+        case ASTNodeType::STAR: {
+            auto n = static_cast<StarNode*>(node);
+            computeFollowpos(n->inner.get(), followpos);
+            for (int p : n->inner->lastpos) {
+                followpos[p].insert(n->inner->firstpos.begin(), n->inner->firstpos.end());
+            }
+            break;
+        }
+        case ASTNodeType::PLUS: {
+            auto n = static_cast<PlusNode*>(node);
+            computeFollowpos(n->inner.get(), followpos);
+            for (int p : n->inner->lastpos) {
+                followpos[p].insert(n->inner->firstpos.begin(), n->inner->firstpos.end());
+            }
+            break;
+        }
+        case ASTNodeType::UNION: {
+            auto n = static_cast<UnionNode*>(node);
+            computeFollowpos(n->left.get(), followpos);
+            computeFollowpos(n->right.get(), followpos);
+            break;
+        }
+        case ASTNodeType::OPTIONAL: {
+            auto n = static_cast<OptionalNode*>(node);
+            computeFollowpos(n->inner.get(), followpos);
+            break;
+        }
+        default: break;
+    }
+}
diff --git a/src/nfa.h b/src/nfa.h
@@ -31,3 +31,14 @@ public:
 class NFABuilder {
 public:
     // Global state counter to ensure unique IDs across all NFAs
+    static int globalStateCounter;
+
+    static std::unique_ptr<NFA> build(ASTNode* root, int regexIdx);
+
+private:
+    static void linearize(ASTNode* node, int& posCounter, std::map<int, unsigned char>& posToChar, std::set<int>& dotPositions);
+    static void computeNullableFirstLast(ASTNode* node);
+    static void computeFollowpos(ASTNode* node, std::map<int, std::set<int>>& followpos);
+};
+
+#endif // NFA_H