From e39d4d2f00c5a331e649731da27ff59f16ad6186 Mon Sep 17 00:00:00 2001
From: Al <albarrentine@gmail.com>
Date: Fri, 24 Feb 2017 02:57:16 -0500
Subject: [PATCH] [parser] check for non-null prev/prev2 before creating
 tag-based features

---
 src/averaged_perceptron_tagger.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/src/averaged_perceptron_tagger.c b/src/averaged_perceptron_tagger.c
index 781b64e0..b4b66588 100644
--- a/src/averaged_perceptron_tagger.c
+++ b/src/averaged_perceptron_tagger.c
@@ -1,7 +1,6 @@
 #include "averaged_perceptron_tagger.h"
 #include "log/log.h"
 
-
 bool averaged_perceptron_tagger_predict(averaged_perceptron_t *model, void *tagger, void *context, cstring_array *features, cstring_array *prev_tag_features, cstring_array *prev2_tag_features, cstring_array *labels, ap_tagger_feature_function feature_function, tokenized_string_t *tokenized) {
 
     // Keep two tags of history in training
@@ -15,6 +14,8 @@ bool averaged_perceptron_tagger_predict(averaged_perceptron_t *model, void *tagg
 
     for (uint32_t i = 0; i < num_tokens; i++) {
         cstring_array_clear(features);
+        cstring_array_clear(prev_tag_features);
+        cstring_array_clear(prev2_tag_features);
 
         if (i > 0) {
             prev = cstring_array_get_string(model->classes, prev_id);
@@ -34,13 +35,17 @@ bool averaged_perceptron_tagger_predict(averaged_perceptron_t *model, void *tagg
         uint32_t fidx;
         const char *feature;
 
-        cstring_array_foreach(prev_tag_features, fidx, feature, {
-            feature_array_add(features, 2, (char *)feature, prev);
-        })
+        if (prev) {
+            cstring_array_foreach(prev_tag_features, fidx, feature, {
+                feature_array_add(features, 2, (char *)feature, prev);
+            })
+        }
 
-        cstring_array_foreach(prev2_tag_features, fidx, feature, {
-            feature_array_add(features, 3, (char *)feature, prev2, prev);
-        })
+        if (prev2) {
+            cstring_array_foreach(prev2_tag_features, fidx, feature, {
+                feature_array_add(features, 3, (char *)feature, prev2, prev);
+            })
+        }
 
         uint32_t guess = averaged_perceptron_predict(model, features);
         char *predicted = cstring_array_get_string(model->classes, guess);