1 files changed, 89 insertions, 0 deletions
diff --git a/src/knowledge/knowledge_get_random_sequence.c b/src/knowledge/knowledge_get_random_sequence.c
new file mode 100644
index 0000000..60a075f
--- /dev/null
+++ b/src/knowledge/knowledge_get_random_sequence.c
@@ -0,0 +1,89 @@
+#include <stdlib.h>
+
+#include "../core/char.h"
+#include "../core/index.h"
+
+#include "../sequence/sequence.h"
+
+#include "../error/error.h"
+
+#include "knowledge.h"
+
+static int weighted_random_pick
+(
+   const struct JH_knowledge_sequence_collection sc [const restrict static 1],
+   const JH_index sum,
+   JH_index result [const restrict static 1]
+)
+{
+   JH_index accumulator, random_number;
+
+   accumulator = 0;
+
+   if (sum == 0)
+   {
+      return -1;
+   }
+
+   random_number = JH_index_random_up_to(sum);
+   /*@ ensures (0 <= random_number <= weights_sum); @*/
+
+   *result = 0;
+
+   for (;;)
+   {
+      accumulator += sc->sequences_ref[*result].occurrences;
+
+      if (accumulator < random_number)
+      {
+         *result += 1;
+      }
+      else
+      {
+         *result = sc->sequences_ref[*result].id;
+
+         return 0;
+      }
+   }
+}
+
+int JH_knowledge_copy_random_swt_sequence
+(
+   const struct JH_knowledge k [const static 1],
+   JH_index sequence [const restrict static 1],
+   const JH_index word_id,
+   const JH_index markov_order,
+   FILE io [const restrict static 1]
+)
+{
+   JH_index sequence_id;
+
+   if
+   (
+      weighted_random_pick
+      (
+         &(k->words[word_id].swt),
+         k->words[word_id].occurrences,
+         &sequence_id
+      ) < 0
+   )
+   {
+      JH_S_PROG_ERROR
+      (
+         io,
+         "Knowledge inconsistency; there are no acceptable markov sequences "
+         "linked to a word that has been picked as being an acceptable pillar."
+      )
+   ;
+      return -1;
+   }
+
+   memcpy
+   (
+      (void *) sequence,
+      (const void *) k->sequences[sequence_id],
+      (((size_t) (markov_order - 1)) * sizeof(JH_index))
+   );
+
+   return 0;
+}