tree_fragment stuff

1 files changed, 115 insertions, 0 deletions

diff --git a/decoder/tree_fragment.cc b/decoder/tree_fragment.cc
new file mode 100644
index 00000000..d5c30f58
--- /dev/null
+++ b/decoder/tree_fragment.cc
@@ -0,0 +1,115 @@
+#include "tree_fragment.h"
+
+#include <cassert>
+
+using namespace std;
+
+namespace cdec {
+
+TreeFragment::TreeFragment(const string& tree, bool allow_frontier_sites) {
+  int bal = 0;
+  const unsigned len = tree.size();
+  unsigned cur = 0;
+  unsigned open = 0, close = 0;
+  for (auto& c : tree) {
+    ++cur;
+    if (c == '(') { ++open; ++bal; }
+    else if (c == ')') {
+      ++close; --bal;
+      if (bal < 1 && cur != len) {
+        cerr << "Badly formed tree detected at column " << cur << " in:\n" << tree << endl;
+        abort();
+      }
+    }
+  }
+  nodes.resize(open);
+  unsigned cp = 0, symp = 0, np = 0;
+  ParseRec(tree, allow_frontier_sites, cp, symp, np, &cp, &symp, &np);
+  root = nodes.back().lhs;
+  //cerr << "ROOT: " << TD::Convert(root & ALL_MASK) << endl;
+  //DebugRec(open - 1, &cerr); cerr << "\n";
+}
+
+void TreeFragment::DebugRec(unsigned cur, ostream* out) const {
+  *out << '(' << TD::Convert(nodes[cur].lhs & ALL_MASK);
+  for (auto& x : nodes[cur].rhs) {
+    *out << ' ';
+    if (IsFrontier(x)) {
+      *out << '[' << TD::Convert(x & ALL_MASK) << ']';
+    } else if (IsInternalNT(x)) {
+      DebugRec(x & ALL_MASK, out);
+    } else { // must be terminal
+      *out << TD::Convert(x);
+    }
+  }
+  *out << ')';
+}
+
+// cp is the character index in the tree
+// np keeps track of the nodes (nonterminals) that have been built
+// symp keeps track of the terminal symbols that have been built
+void TreeFragment::ParseRec(const string& tree, bool afs, unsigned cp, unsigned symp, unsigned np, unsigned* pcp, unsigned* psymp, unsigned* pnp) {
+  if (tree[cp] != '(') {
+    cerr << "Expected ( at " << cp << endl;
+    abort();
+  }
+  const unsigned i = symp;
+  vector<unsigned> rhs; // w | 0 = terminal, w | NT_BIT, index | FRONTIER_BIT
+  ++cp;
+  while(tree[cp] == ' ') { ++cp; }
+  const unsigned nt_start = cp;
+  while(tree[cp] != ' ' && tree[cp] != '(' && tree[cp] != ')') { ++cp; }
+  const unsigned nt_end = cp;
+  while(tree[cp] == ' ') { ++cp; }
+  while (tree[cp] != ')') {
+    if (tree[cp] == '(') {
+      // recursively call parser to deal with constituent
+      ParseRec(tree, afs, cp, symp, np, &cp, &symp, &np);
+      unsigned ind = np - 1;
+      rhs.push_back(ind | NT_BIT);
+    } else { // deal with terminal / nonterminal substitution
+      ++symp;
+      assert(tree[cp] != ' ');
+      const unsigned t_start = cp;
+      while(tree[cp] != ' ' && tree[cp] != ')' && tree[cp] != '(') { ++cp; }
+      const unsigned t_end = cp;
+      while(tree[cp] == ' ') { ++cp; }
+      // TODO: add a terminal symbol to the current edge
+      const bool is_terminal = tree[t_start] != '[' || (t_end - t_start < 3 || tree[t_end - 1] != ']');
+      if (is_terminal) {
+        const unsigned term = TD::Convert(tree.substr(t_start, t_end - t_start));
+        rhs.push_back(term);
+        // cerr << "T='" << TD::Convert(term) << "'\n";
+        ++terminals;
+      } else { // frontier site (NT but no recursion)
+        const unsigned nt = TD::Convert(tree.substr(t_start + 1, t_end - t_start - 2)) | FRONTIER_BIT;
+        rhs.push_back(nt);
+        ++frontier_sites;
+        // cerr << "FRONT-NT=[" << TD::Convert(nt & ALL_MASK) << "]\n";
+        if (!afs) {
+          cerr << "Frontier sites not allowed in input: " << tree << endl;
+          abort();
+        }
+      } 
+    }
+  } // continuent has completed, cp is at ), build node
+  const unsigned j = symp; // span from (i,j)
+  // add an internal non-terminal symbol
+  const unsigned nt = TD::Convert(tree.substr(nt_start, nt_end - nt_start)) | NT_BIT;
+  nodes[np] = TreeFragmentProduction(nt, rhs);
+  //cerr << np << " production(" << i << "," << j << ")=  " << TD::Convert(nt & ALL_MASK) << " -->";
+  //for (auto& x : rhs) {
+  //  cerr << ' ';
+  //  if (IsFrontier(x)) cerr << '*';
+  //  if (IsInternalNT(x)) cerr << TD::Convert(nodes[x & ALL_MASK].lhs & ALL_MASK); else
+  //    cerr << TD::Convert(x & ALL_MASK);
+  //}
+  //cerr << "\n   "; DebugRec(np,&cerr); cerr << endl;
+  ++cp;
+  while(tree[cp] == ' ' && cp < tree.size()) { ++cp; }
+  *pcp = cp;
+  *pnp = np + 1;
+  *psymp = symp;
+}
+
+}