From 4e62908a1757f83ff703399252ad50758c4eb237 Mon Sep 17 00:00:00 2001
From: Patrick Simianer <patrick@lilt.com>
Date: Tue, 24 Feb 2026 17:18:29 +0100
Subject: Replace silent rescue with explicit type check in Item constructor

When creating an Item from a Rule (not an Item), tail_spans doesn't exist.
Check with is_a?(Item) instead of catching the exception silently.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 prototype/parse.rb | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

(limited to 'prototype/parse.rb')

diff --git a/prototype/parse.rb b/prototype/parse.rb
index adf2b91..40a69e7 100644
--- a/prototype/parse.rb
+++ b/prototype/parse.rb
@@ -90,14 +90,10 @@ class Item < Grammar::Rule
     rule_or_item.rhs.each_with_index { |x,i| # duplicate rhs partially
       @rhs << x
       if x.class == Grammar::NT
-        begin
-          if i >= dot
-            @tail_spans[i] = Span.new(-1, -1)
-          else
-            @tail_spans[i] = rule_or_item.tail_spans[i].dup
-          end
-        rescue
+        if i >= dot || !rule_or_item.is_a?(Item)
           @tail_spans[i] = Span.new(-1, -1)
+        else
+          @tail_spans[i] = rule_or_item.tail_spans[i].dup
         end
       end
     }
-- 
cgit v1.2.3


From 44f225d0642d2ecf13f533f68b9ae12d849809ea Mon Sep 17 00:00:00 2001
From: Patrick Simianer <patrick@lilt.com>
Date: Thu, 26 Feb 2026 19:29:18 +0100
Subject: Fix two bugs in prototype parser

1. Inner visit at span (0,1) yielded no sub-spans because
   visit(1, 0, 1, 1) iterates span from 1 to r-x=0, which is
   empty. This prevented unary rules like [S] ||| [X,1] from
   completing at the leftmost span, so S(0,1) was never created.
   Drop the x=1 parameter (default x=0); scan already handles
   bounds checking.

2. Self-filling step searched remaining_items for unary NT rules,
   but those rules could be absent if consumed (advanced) during
   the parse loop. Look up grammar.start_nt directly instead,
   which covers all cases.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 prototype/parse.rb | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

(limited to 'prototype/parse.rb')

diff --git a/prototype/parse.rb b/prototype/parse.rb
index 40a69e7..1741030 100644
--- a/prototype/parse.rb
+++ b/prototype/parse.rb
@@ -152,7 +152,7 @@ def Parse::parse input, n, active_chart, passive_chart, grammar
     while !active_chart.at(i,j).empty?
       active_item = active_chart.at(i,j).pop
       advanced = false
-      visit(1, i, j, 1) { |k,l|
+      visit(1, i, j) { |k,l|
         if passive_chart.has active_item.rhs[active_item.dot].symbol, k, l
           if k == active_item.right
             new_item = Item.new active_item, active_item.left, l, active_item.dot+1
@@ -182,16 +182,15 @@ def Parse::parse input, n, active_chart, passive_chart, grammar
 
     # 'self-filling' step
     new_symbols.each { |s|
-      remaining_items.each { |item|
-        next if item.dot!=0
-        next if item.rhs[item.dot].class!=Grammar::NT
-        if item.rhs[item.dot].symbol == s
-          new_item = Item.new item, i, j, item.dot+1
-          new_item.tail_spans[new_item.dot-1] = Span.new(i,j)
-          if new_item.dot==new_item.rhs.size
-            new_symbols << new_item.lhs.symbol if !new_symbols.include? new_item.lhs.symbol
-            passive_chart.add new_item, i, j
-          end
+      grammar.start_nt.each { |r|
+        next if r.rhs.size > j-i
+        next if r.rhs.first.class!=Grammar::NT
+        next if r.rhs.first.symbol != s
+        new_item = Item.new r, i, j, 1
+        new_item.tail_spans[0] = Span.new(i,j)
+        if new_item.dot==new_item.rhs.size
+          new_symbols << new_item.lhs.symbol if !new_symbols.include? new_item.lhs.symbol
+          passive_chart.add new_item, i, j
         end
       }
     }
-- 
cgit v1.2.3