It's starting to "properly" reply...

The ACSL coverage is far behind though.

6 files changed, 198 insertions, 208 deletions

diff --git a/src/sequence/sequence.c b/src/sequence/sequence.c
index f3c3b46..78a5aad 100644
--- a/src/sequence/sequence.c
+++ b/src/sequence/sequence.c
@@ -5,74 +5,6 @@
 
 #include "sequence.h"
 
-/*
- * Bypass rendundant ZoO_START_OF_SEQUENCE_ID at the start of a sequence.
- */
-/*@
-   requires
-   (
-      \valid(sequence+ (0 .. sequence_length))
-      || (sequence_length == 0)
-   );
-   requires \separated(sequence, sequence_offset);
-
-   assigns (*sequence_offset);
-
-   ensures (*sequence_offset < sequence_length);
-
-   ensures
-   (
-      (*sequence_offset == 0)
-      || (sequence[0 .. *sequence_offset] == ZoO_START_OF_SEQUENCE_ID)
-   );
-
-   ensures
-   (
-      (*sequence_offset == sequence_length)
-      || (sequence[*sequence_offset + 1] != ZoO_START_OF_SEQUENCE_ID)
-   );
-
-@*/
-static void bypass_redundant_sos
-(
-   const ZoO_index sequence [const restrict],
-   const size_t sequence_length,
-   size_t sequence_offset [const restrict static 1]
-)
-{
-   ZoO_index i;
-
-   *sequence_offset = 0;
-
-   /*@
-      loop invariant 0 <= i <= sequence_length;
-      loop invariant (*sequence_offset <= i);
-      loop invariant
-      (
-         (*sequence_offset == 0)
-         || (sequence[*sequence_offset] == ZoO_START_OF_SEQUENCE_ID)
-      );
-      loop invariant
-         (
-            (i == 0) || (sequence[0 .. (i - 1)] == ZoO_START_OF_SEQUENCE_ID)
-         );
-      loop assigns i, *sequence_offset;
-      loop variant (sequence_length - i);
-   @*/
-   for (i = 0; i < sequence_length; ++i)
-   {
-      if (sequence[i] != ZoO_START_OF_SEQUENCE_ID)
-      {
-         return;
-      }
-      else if (sequence[i] == ZoO_START_OF_SEQUENCE_ID)
-      {
-         *sequence_offset = i;
-      }
-   }
-}
-
-
 /* See "sequence.h" */
 /*@
    requires
@@ -91,80 +23,28 @@ static void bypass_redundant_sos
 @*/
 int ZoO_sequence_cmp
 (
-   const ZoO_index sequence_a [const],
-   size_t sequence_a_length,
-   const ZoO_index sequence_b [const],
-   size_t sequence_b_length
+   const ZoO_index sequence_a [const restrict static 1],
+   const ZoO_index sequence_b [const restrict static 1],
+   const ZoO_index length
 )
 {
-   size_t min_length, a, b;
-   size_t a_offset, b_offset;
-   size_t i;
-   /*@ ghost size_t actual_a_length, actual_b_length; @*/
-
-   bypass_redundant_sos(sequence_a, sequence_a_length, &a_offset);
-   bypass_redundant_sos(sequence_b, sequence_b_length, &b_offset);
+   ZoO_index i, a, b;
 
-   /*@ ghost actual_a_length = sequence_a_length; @*/
-   /*@ ghost actual_b_length = sequence_b_length; @*/
-
-   /*@ assert (a_offset <= sequence_a_length); @*/
-   sequence_a_length -= a_offset;
-   /*@ assert (b_offset <= sequence_b_length); @*/
-   sequence_b_length -= b_offset;
-
-   if (sequence_a_length < sequence_b_length)
-   {
-      min_length = sequence_a_length;
-   }
-   else
+   for (i = 0; i < length; ++i)
    {
-      min_length = sequence_b_length;
-   }
-
-   /*@ assert (min_length <= sequence_a_length); @*/
-   /*@ assert (min_length <= sequence_b_length); @*/
-
-   /*@ assert (min_length + a_offset <= actual_a_length); @*/
-   /*@ assert (min_length + b_offset <= actual_b_length); @*/
-
-   /*@
-      loop invariant 0 <= i <= min_length;
-      loop assigns i;
-      loop variant (min_length - i);
-   @*/
-   for (i = 0; i < min_length; ++i)
-   {
-      /*@ assert ((i + a_offset) < actual_a_length); @*/
-      a = sequence_a[i + a_offset];
-      /*@ assert ((i + b_offset) < actual_b_length); @*/
-      b = sequence_b[i + b_offset];
+      a = sequence_a[i];
+      b = sequence_b[i];
 
       if (a < b)
       {
          return -1;
       }
-      else if (b > a)
+      else if (a > b)
       {
          return 1;
       }
-      else if ((a == ZoO_END_OF_SEQUENCE_ID) && (b == ZoO_END_OF_SEQUENCE_ID))
-      {
-         return 0;
-      }
    }
 
-   if (sequence_a_length > sequence_b_length)
-   {
-      return 1;
-   }
-   else if (sequence_a_length < sequence_b_length)
-   {
-      return -1;
-   }
-   else
-   {
-      return 0;
-   }
+   return 0;
 }
 
diff --git a/src/sequence/sequence.h b/src/sequence/sequence.h
index 129c457..9239336 100644
--- a/src/sequence/sequence.h
+++ b/src/sequence/sequence.h
@@ -7,7 +7,7 @@
 #include "../core/char_types.h"
 #include "../core/index_types.h"
 
-#include "../pipe/pipe.h"
+#include "../error/error.h"
 
 #include "../knowledge/knowledge_types.h"
 
@@ -15,16 +15,32 @@
 
 /*@
    requires \valid(sequence);
-   requires \valid(*sequence);
+   requires (\block_length(sequence) >= 1);
    requires \valid(sequence_capacity);
+   requires (\block_length(sequence) >= 1);
    requires \valid(io);
 
    requires (((*sequence_capacity) * sizeof(ZoO_index)) <= SIZE_MAX);
    requires ((sequence_required_capacity * sizeof(ZoO_index)) <= SIZE_MAX);
 
-   requires \separated(sequence, *sequence, sequence_capacity, io);
+   requires
+      \separated
+      (
+         (sequence+ (0 .. \block_length(sequence))),
+         ((*sequence)+ (0 .. \block_length(*sequence))),
+         (sequence_capacity+ (0 ..\block_length(sequence_capacity))),
+         (io+ (0 ..\block_length(io)))
+      );
+
+   ensures
+      \separated
+      (
+         (sequence+ (0 .. \block_length(sequence))),
+         ((*sequence)+ (0 .. \block_length(*sequence))),
+         (sequence_capacity+ (0 ..\block_length(sequence_capacity))),
+         (io+ (0 ..\block_length(io)))
+      );
 
-   ensures \separated(sequence, *sequence, sequence_capacity, io);
    ensures (((*sequence_capacity) * sizeof(ZoO_index)) <= SIZE_MAX);
    ensures ((sequence_required_capacity * sizeof(ZoO_index)) <= SIZE_MAX);
    ensures \valid(sequence);
@@ -70,7 +86,7 @@ int ZoO_sequence_ensure_capacity
    ZoO_index * sequence [const restrict static 1],
    size_t sequence_capacity [const restrict static 1],
    const size_t sequence_required_capacity,
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 );
 
 int ZoO_sequence_from_undercase_string
@@ -81,7 +97,7 @@ int ZoO_sequence_from_undercase_string
    ZoO_index * sequence [const restrict static 1],
    size_t sequence_capacity [const restrict static 1],
    size_t sequence_length [const restrict static 1],
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 );
 
 /*
@@ -114,7 +130,7 @@ int ZoO_sequence_create_from
    ZoO_index * sequence [const restrict static 1],
    size_t sequence_capacity [const restrict static 1],
    size_t sequence_length [const restrict static 1],
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 );
 
 /*@
@@ -125,7 +141,15 @@ int ZoO_sequence_create_from
    requires \valid(io);
    requires (((*sequence_length) * sizeof(ZoO_index)) <= SIZE_MAX);
    requires (((*sequence_capacity) * sizeof(ZoO_index)) <= SIZE_MAX);
-   requires \separated(sequence, *sequence, sequence_capacity, sequence_length, io);
+   requires
+      \separated
+      (
+         (sequence+ (0 .. \block_length(sequence))),
+         ((*sequence)+ (0 .. \block_length(*sequence))),
+         (sequence_capacity+ (0 ..\block_length(sequence_capacity))),
+         (sequence_length+ (0 ..\block_length(sequence_length))),
+         (io+ (0 ..\block_length(io)))
+      );
 
    assigns (*sequence_length);
    assigns (*sequence[0]);
@@ -138,7 +162,15 @@ int ZoO_sequence_create_from
    ensures \valid(io);
    ensures (((*sequence_length) * sizeof(ZoO_index)) <= SIZE_MAX);
    ensures (((*sequence_capacity) * sizeof(ZoO_index)) <= SIZE_MAX);
-   ensures \separated(sequence, *sequence, sequence_capacity, sequence_length, io);
+   ensures
+      \separated
+      (
+         (sequence+ (0 .. \block_length(sequence))),
+         ((*sequence)+ (0 .. \block_length(*sequence))),
+         (sequence_capacity+ (0 ..\block_length(sequence_capacity))),
+         (sequence_length+ (0 ..\block_length(sequence_length))),
+         (io+ (0 ..\block_length(io)))
+      );
 
    ensures ((\result == 0) || (\result == -1));
 
@@ -157,7 +189,7 @@ int ZoO_sequence_create_from
    ensures ((\result == 0) ==> (*sequence_length > \old(*sequence_length)));
 
    ensures ((\result == -1) ==> ((*sequence_length) == \old(*sequence_length)));
-   ensures ((\result == -1) ==> ((*sequence[0]) == \old(*sequence[0])));
+   ensures ((\result == -1) ==> (((*sequence)[0]) == \old((*sequence)[0])));
    ensures
       (
          (\result == -1) ==>
@@ -178,7 +210,7 @@ int ZoO_sequence_append_left
    ZoO_index * sequence [const restrict static 1],
    size_t sequence_capacity [const restrict static 1],
    size_t sequence_length [const restrict static 1],
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 );
 
 /*@
@@ -189,10 +221,18 @@ int ZoO_sequence_append_left
    requires \valid(io);
    requires (((*sequence_length) * sizeof(ZoO_index)) <= SIZE_MAX);
    requires (((*sequence_capacity) * sizeof(ZoO_index)) <= SIZE_MAX);
-   requires \separated(sequence, *sequence, sequence_capacity, sequence_length, io);
+   requires
+      \separated
+      (
+         (sequence+ (0 .. \block_length(sequence))),
+         ((*sequence)+ (0 .. \block_length(*sequence))),
+         (sequence_capacity+ (0 ..\block_length(sequence_capacity))),
+         (sequence_length+ (0 ..\block_length(sequence_length))),
+         (io+ (0 ..\block_length(io)))
+      );
 
    assigns (*sequence_length);
-   assigns (*sequence[0]);
+   assigns ((*sequence)[0]);
    assigns (*sequence_capacity);
 
    ensures \valid(sequence);
@@ -202,7 +242,15 @@ int ZoO_sequence_append_left
    ensures \valid(io);
    ensures (((*sequence_length) * sizeof(ZoO_index)) <= SIZE_MAX);
    ensures (((*sequence_capacity) * sizeof(ZoO_index)) <= SIZE_MAX);
-   ensures \separated(sequence, *sequence, sequence_capacity, sequence_length, io);
+   ensures
+      \separated
+      (
+         (sequence+ (0 .. \block_length(sequence))),
+         ((*sequence)+ (0 .. \block_length(*sequence))),
+         (sequence_capacity+ (0 ..\block_length(sequence_capacity))),
+         (sequence_length+ (0 ..\block_length(sequence_length))),
+         (io+ (0 ..\block_length(io)))
+      );
 
    ensures ((\result == 0) || (\result == -1));
 
@@ -221,7 +269,7 @@ int ZoO_sequence_append_left
    ensures ((\result == 0) ==> (*sequence_length > \old(*sequence_length)));
 
    ensures ((\result == -1) ==> ((*sequence_length) == \old(*sequence_length)));
-   ensures ((\result == -1) ==> ((*sequence[0]) == \old(*sequence[0])));
+   ensures ((\result == -1) ==> (((*sequence)[0]) == \old((*sequence)[0])));
    ensures
       (
          (\result == -1) ==>
@@ -242,7 +290,7 @@ int ZoO_sequence_append_right
    const ZoO_index word_id,
    size_t sequence_capacity [const restrict static 1],
    size_t sequence_length [const restrict static 1],
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 );
 
 /*
@@ -265,9 +313,19 @@ int ZoO_sequence_append_right
 int ZoO_sequence_cmp
 (
    const ZoO_index sequence_a [const],
-   size_t sequence_a_length,
    const ZoO_index sequence_b [const],
-   size_t sequence_b_length
+   const ZoO_index length
+);
+
+int ZoO_sequence_to_undercase_string
+(
+   const ZoO_index sequence [const restrict static 1],
+   const size_t sequence_length,
+   struct ZoO_knowledge k [const restrict static 1],
+   ZoO_char * destination [const restrict static 1],
+   size_t destination_capacity [const restrict static 1],
+   size_t destination_length [const restrict static 1],
+   FILE io [const restrict static 1]
 );
 
 #endif
diff --git a/src/sequence/sequence_append.c b/src/sequence/sequence_append.c
index 604d251..81dfa99 100644
--- a/src/sequence/sequence_append.c
+++ b/src/sequence/sequence_append.c
@@ -5,7 +5,7 @@
 
 #include "../core/index.h"
 
-#include "../pipe/pipe.h"
+#include "../error/error.h"
 
 #include "sequence.h"
 
@@ -16,10 +16,14 @@
 /*@
    requires \valid(required_capacity);
    requires \valid(io);
-   requires \separated(required_capacity, io);
+   requires
+      \separated
+      (
+         (required_capacity+ (0 .. \block_length(required_capacity))),
+         (io+ (0 .. \block_length(io)))
+      );
 
    assigns \result;
-
    assigns (*required_capacity);
 
    ensures ((\result == 0) || (\result == -1));
@@ -27,7 +31,12 @@
    ensures \valid(required_capacity);
    ensures \valid(io);
 
-   ensures \separated(required_capacity, io);
+   ensures
+      \separated
+      (
+         (required_capacity+ (0 .. \block_length(required_capacity))),
+         (io+ (0 .. \block_length(io)))
+      );
 
    ensures
       (
@@ -51,7 +60,7 @@
 static int increment_required_capacity
 (
    size_t required_capacity [const restrict static 1],
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 )
 {
    if
@@ -92,7 +101,7 @@ int ZoO_sequence_ensure_capacity
    ZoO_index * sequence [const restrict static 1],
    size_t sequence_capacity [const restrict static 1],
    const size_t sequence_required_capacity,
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 )
 {
    ZoO_index * new_sequence;
@@ -146,7 +155,7 @@ int ZoO_sequence_append_left
    ZoO_index * sequence [const restrict static 1],
    size_t sequence_capacity [const restrict static 1],
    size_t sequence_length [const restrict static 1],
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 )
 {
    if (increment_required_capacity(sequence_length, io) < 0)
@@ -171,17 +180,17 @@ int ZoO_sequence_append_left
       return -1;
    }
 
-   /*@ assert *sequence_length >= 0; @*/
+   /*@ assert (*sequence_length) >= 0; @*/
 
-   if (*sequence_length > 1)
+   if ((*sequence_length) > 1)
    {
       /*@ assert(((*sequence_length) * sizeof(ZoO_index)) <= SIZE_MAX); @*/
 
       #ifndef ZoO_RUNNING_FRAMA_C
       memmove
       (
-         (void *) (*sequence + 1),
-         (const void *) sequence,
+         (void *) ((*sequence) + 1),
+         (const void *) (*sequence),
          (((*sequence_length) - 1) * sizeof(ZoO_index))
       );
       #endif
@@ -198,7 +207,7 @@ int ZoO_sequence_append_right
    const ZoO_index word_id,
    size_t sequence_capacity [const restrict static 1],
    size_t sequence_length [const restrict static 1],
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 )
 {
    if (increment_required_capacity(sequence_length, io) < 0)
@@ -206,7 +215,7 @@ int ZoO_sequence_append_right
       return -1;
    }
 
-   /*@ assert ((*sequence_length * sizeof(ZoO_index)) <= SIZE_MAX); @*/
+   /*@ assert (((*sequence_length) * sizeof(ZoO_index)) <= SIZE_MAX); @*/
 
    if
    (
@@ -224,9 +233,9 @@ int ZoO_sequence_append_right
       return -1;
    }
 
-   /*@ assert (*sequence_length >= 1); @*/
-   (*sequence)[*sequence_length - 1] = word_id;
-   /*@ assert (*sequence_length >= 1); @*/
+   /*@ assert ((*sequence_length) >= 1); @*/
+   (*sequence)[(*sequence_length) - 1] = word_id;
+   /*@ assert ((*sequence_length) >= 1); @*/
 
    return 0;
 }
diff --git a/src/sequence/sequence_creation.c b/src/sequence/sequence_creation.c
index 1f20262..9556693 100644
--- a/src/sequence/sequence_creation.c
+++ b/src/sequence/sequence_creation.c
@@ -5,7 +5,7 @@
 
 #include "../core/index.h"
 
-#include "../pipe/pipe.h"
+#include "../error/error.h"
 
 #include "../knowledge/knowledge.h"
 
@@ -40,7 +40,7 @@ static int extend_left
    size_t sequence_length [const restrict static 1],
    const ZoO_index markov_order,
    struct ZoO_knowledge k [const restrict static 1],
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 )
 {
    ZoO_index sequence_id, word_id;
@@ -62,7 +62,8 @@ static int extend_left
    {
       (void) ZoO_knowledge_unlock_access(k, io);
 
-      /* TODO: Err message. */
+      ZoO_S_ERROR(io, "Could not find matching TWS sequence.");
+
       return -1;
    }
 
@@ -83,7 +84,7 @@ static int extend_left
    {
       (void) ZoO_knowledge_unlock_access(k, io);
 
-      /* TODO: Err message. */
+      ZoO_S_ERROR(io, "Could not find matching TWS target.");
 
       return -1;
    }
@@ -138,7 +139,7 @@ static int complete_left_part_of_sequence
    const ZoO_index markov_order,
    size_t credits [const restrict],
    struct ZoO_knowledge k [const restrict static 1],
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 )
 {
    for (;;)
@@ -159,7 +160,7 @@ static int complete_left_part_of_sequence
          )
          {
             /* We are sure *sequence[0] is defined. */
-            if (*sequence[0] == ZoO_START_OF_SEQUENCE_ID)
+            if ((*sequence)[0] == ZoO_START_OF_SEQUENCE_ID)
             {
                /*
                 * We failed to add a word, but it was because none should have
@@ -176,7 +177,7 @@ static int complete_left_part_of_sequence
       else
       {
          /* No more credits available, the sequence will have to start here. */
-         *sequence[0] = ZoO_START_OF_SEQUENCE_ID;
+         (*sequence)[0] = ZoO_START_OF_SEQUENCE_ID;
 
          return 0;
       }
@@ -187,7 +188,7 @@ static int complete_left_part_of_sequence
       }
 
       /* We are sure *sequence[0] is defined. */
-      switch (*sequence[0])
+      switch ((*sequence)[0])
       {
          case ZoO_END_OF_SEQUENCE_ID:
             ZoO_S_WARNING
@@ -196,7 +197,7 @@ static int complete_left_part_of_sequence
                "END OF LINE was added at the left part of an sequence."
             );
 
-            *sequence[0] = ZoO_START_OF_SEQUENCE_ID;
+            (*sequence)[0] = ZoO_START_OF_SEQUENCE_ID;
             return 0;
 
          case ZoO_START_OF_SEQUENCE_ID:
@@ -237,7 +238,7 @@ static int extend_right
    size_t sequence_length [const restrict static 1],
    const ZoO_index markov_order,
    struct ZoO_knowledge k [const restrict static 1],
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 )
 {
    ZoO_index sequence_id, word_id;
@@ -342,7 +343,7 @@ static int complete_right_part_of_sequence
    const ZoO_index markov_order,
    size_t credits [const restrict],
    struct ZoO_knowledge k [const restrict static 1],
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 )
 {
    for (;;)
@@ -363,7 +364,7 @@ static int complete_right_part_of_sequence
          )
          {
             /* Safe: (> sequence_length 1) */
-            if (*sequence[(*sequence_length - 1)] == ZoO_END_OF_SEQUENCE_ID)
+            if ((*sequence)[(*sequence_length - 1)] == ZoO_END_OF_SEQUENCE_ID)
             {
                /*
                 * We failed to add a word, but it was because none should have
@@ -380,7 +381,7 @@ static int complete_right_part_of_sequence
       else
       {
          /* No more credits available, we end the sequence. */
-         *sequence[(*sequence_length - 1)] = ZoO_END_OF_SEQUENCE_ID;
+         (*sequence)[((*sequence_length) - 1)] = ZoO_END_OF_SEQUENCE_ID;
 
          return 0;
       }
@@ -391,7 +392,7 @@ static int complete_right_part_of_sequence
       }
 
       /* Safe: (> sequence_length 1) */
-      switch (*sequence[(*sequence_length - 1)])
+      switch ((*sequence)[((*sequence_length) - 1)])
       {
          case ZoO_START_OF_SEQUENCE_ID:
             ZoO_S_WARNING
@@ -400,7 +401,7 @@ static int complete_right_part_of_sequence
                "END OF LINE was added at the right part of an sequence."
             );
 
-            *sequence[(*sequence_length - 1)] = ZoO_END_OF_SEQUENCE_ID;
+            (*sequence)[((*sequence_length) - 1)] = ZoO_END_OF_SEQUENCE_ID;
             return 0;
 
          case ZoO_END_OF_SEQUENCE_ID:
@@ -438,7 +439,7 @@ static int initialize_sequence
    const ZoO_index initial_word,
    const ZoO_index markov_order,
    struct ZoO_knowledge k [const static 1],
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 )
 {
    sequence[(markov_order - 1)] = initial_word;
@@ -467,6 +468,23 @@ static int initialize_sequence
       return -1;
    }
 
+   if (ZoO_DEBUG_SEQUENCE_CREATION_INIT)
+   {
+      ZoO_index i;
+
+      for (i = 0; i < markov_order; ++i)
+      {
+         ZoO_DEBUG
+         (
+            io,
+            ZoO_DEBUG_SEQUENCE_CREATION_INIT,
+            "sequence[%u]: %u",
+            i,
+            sequence[i]
+         );
+      }
+   }
+
    (void) ZoO_knowledge_unlock_access(k, io);
 
    return 0;
@@ -486,9 +504,11 @@ int ZoO_sequence_create_from
    ZoO_index * sequence [const restrict static 1],
    size_t sequence_capacity [const restrict static 1],
    size_t sequence_length [const restrict static 1],
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 )
 {
+   size_t i;
+
    if
    (
       ZoO_sequence_ensure_capacity
@@ -517,6 +537,8 @@ int ZoO_sequence_create_from
       ) < 0
    )
    {
+      ZoO_S_ERROR(io, "Failed to create start of new sequence.");
+
       *sequence_length = 0;
 
       return -2;
@@ -538,6 +560,8 @@ int ZoO_sequence_create_from
       ) < 0
    )
    {
+      ZoO_S_ERROR(io, "Failed to create right part of sequence.");
+
       *sequence_length = 0;
 
       return -3;
@@ -557,6 +581,8 @@ int ZoO_sequence_create_from
       ) < 0
    )
    {
+      ZoO_S_ERROR(io, "Failed to create left part of sequence.");
+
       *sequence_length = 0;
 
       return -4;
diff --git a/src/sequence/sequence_from_string.c b/src/sequence/sequence_from_string.c
index 6acfdc2..e493bbc 100644
--- a/src/sequence/sequence_from_string.c
+++ b/src/sequence/sequence_from_string.c
@@ -6,7 +6,7 @@
 #include "../core/char.h"
 #include "../core/index.h"
 
-#include "../pipe/pipe.h"
+#include "../error/error.h"
 
 #include "../knowledge/knowledge.h"
 
@@ -25,17 +25,12 @@ static int add_word_to_sequence
    size_t sequence_capacity [const restrict static 1],
    size_t sequence_length [const restrict static 1],
    struct ZoO_knowledge k [const restrict static 1],
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 )
 {
    ZoO_index word_id;
    ZoO_char * stored_word;
 
-   if (word_length == 0)
-   {
-      return 0;
-   }
-
    (void) ZoO_knowledge_lock_access(k, io);
 
    if
@@ -105,11 +100,6 @@ static int find_word
       i += 1;
    }
 
-   if (i >= string_length)
-   {
-      return -1;
-   }
-
    *word_length = (i - *word_start);
 
    return 0;
@@ -128,7 +118,7 @@ int ZoO_sequence_from_undercase_string
    ZoO_index * sequence [const restrict static 1],
    size_t sequence_capacity [const restrict static 1],
    size_t sequence_length [const restrict static 1],
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 )
 {
    size_t word_start, word_length;
@@ -136,9 +126,16 @@ int ZoO_sequence_from_undercase_string
 
    i = 0;
 
-   *sequence = (ZoO_index *) NULL;
    *sequence_length = 0;
 
+   ZoO_DEBUG
+   (
+      io,
+      ZoO_DEBUG_SEQUENCE_FROM_STRING,
+      "Converting string of size %lu to sequence.",
+      string_length
+   );
+
    if
    (
       ZoO_sequence_append_right
@@ -151,16 +148,34 @@ int ZoO_sequence_from_undercase_string
       ) < 0
    )
    {
+      *sequence_length = 0;
+
       return -1;
    }
 
+   ZoO_S_DEBUG
+   (
+      io,
+      ZoO_DEBUG_SEQUENCE_FROM_STRING,
+      "[SOS] added to sequence."
+   );
+
    while (i < string_length)
    {
-      if (find_word(string, i, string_length, &word_start, &word_length) < 0)
+      if (find_word(string, string_length, i, &word_start, &word_length) < 0)
       {
          break;
       }
 
+      ZoO_DEBUG
+      (
+         io,
+         ZoO_DEBUG_SEQUENCE_FROM_STRING,
+         "Word of size %lu found in string at index %lu.",
+         word_length,
+         word_start
+      );
+
       if
       (
          add_word_to_sequence
@@ -176,8 +191,6 @@ int ZoO_sequence_from_undercase_string
          ) < 0
       )
       {
-         free((void *) *sequence);
-         *sequence = (ZoO_index *) NULL;
          *sequence_length = 0;
 
          return -1;
@@ -198,9 +211,6 @@ int ZoO_sequence_from_undercase_string
       ) < 0
    )
    {
-      free((void *) *sequence);
-
-      *sequence = (ZoO_index *) NULL;
       *sequence_length = 0;
 
       return -1;
diff --git a/src/sequence/sequence_to_string.c b/src/sequence/sequence_to_string.c
index 96bd521..919ef0b 100644
--- a/src/sequence/sequence_to_string.c
+++ b/src/sequence/sequence_to_string.c
@@ -6,7 +6,7 @@
 #include "../core/char.h"
 #include "../core/index.h"
 
-#include "../pipe/pipe.h"
+#include "../error/error.h"
 
 #include "../knowledge/knowledge.h"
 
@@ -20,7 +20,7 @@ static int ensure_string_capacity
    ZoO_char * string [const restrict static 1],
    size_t string_capacity [const restrict static 1],
    const size_t string_required_capacity,
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 )
 {
    ZoO_char * new_string;
@@ -61,10 +61,10 @@ static int increment_required_capacity
 (
    size_t current_capacity [const restrict static 1],
    const size_t increase_factor,
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 )
 {
-   if ((ZoO_INDEX_MAX - increase_factor) > *current_capacity)
+   if ((ZoO_INDEX_MAX - increase_factor) < *current_capacity)
    {
       ZoO_S_ERROR
       (
@@ -78,7 +78,7 @@ static int increment_required_capacity
 
    *current_capacity += increase_factor;
 
-   if ((SIZE_MAX / sizeof(ZoO_char)) > *current_capacity)
+   if ((SIZE_MAX / sizeof(ZoO_char)) < *current_capacity)
    {
       *current_capacity -= increase_factor;
 
@@ -102,13 +102,18 @@ static int add_word
    ZoO_char * destination [const restrict static 1],
    size_t destination_capacity [const restrict static 1],
    size_t destination_length [const restrict static 1],
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 )
 {
 	const ZoO_char * word;
 	ZoO_index word_size;
    size_t insertion_point;
 
+   if (word_id < ZoO_RESERVED_IDS_COUNT)
+   {
+      return 0;
+   }
+
 	(void) ZoO_knowledge_lock_access(k, io);
 	ZoO_knowledge_get_word(k, word_id, &word, &word_size);
 	(void) ZoO_knowledge_unlock_access(k, io);
@@ -155,15 +160,17 @@ int ZoO_sequence_to_undercase_string
 (
    const ZoO_index sequence [const restrict static 1],
    const size_t sequence_length,
-   ZoO_char * destination [const restrict static 1],
    struct ZoO_knowledge k [const restrict static 1],
+   ZoO_char * destination [const restrict static 1],
    size_t destination_capacity [const restrict static 1],
    size_t destination_length [const restrict static 1],
-   const struct ZoO_pipe io [const restrict static 1]
+   FILE io [const restrict static 1]
 )
 {
    size_t i;
 
+   *destination_length = 0;
+
    for (i = 0; i < sequence_length; ++i)
    {
       if