diff --git a/src/templates_text/templator_text.org b/src/templates_text/templator_text.org
index 0c04249..7ad22b1 100644
--- a/src/templates_text/templator_text.org
+++ b/src/templates_text/templator_text.org
@@ -91,6 +91,11 @@ typedef struct $group$_s {
 
 * Template for general structure in text back end
 
+   Polymorphism of the ~trexio_t~ type is handled by ensuring that the
+   corresponding types for all back ends can be safely casted to
+   ~trexio_t~. This is done by making the back-end structs start with
+   ~trexio_t parent~ attribute:
+
     #+begin_src c :tangle struct_text_group.h
 typedef struct trexio_text_s {
   trexio_t   parent ;
@@ -333,12 +338,7 @@ trexio_text_read_$group$ (trexio_text_t* const file)
 
         rc = fscanf(f, "%u", &($group$->rank_$group_dset$));
         if (rc != 1) {
-          FREE(buffer);
-          fclose(f);
-          /* Set pointer to the struct so that the garbage collector can do the job on file handle */
-          file->$group$ = $group$;
-          rc_free = trexio_text_free_$group$(file);
-          assert(rc_free == TREXIO_SUCCESS);
+          trexio_text_free_read_$group$(buffer, f, file, $group$);
           return NULL;
         }
 
@@ -349,24 +349,14 @@ trexio_text_read_$group$ (trexio_text_t* const file)
           uint32_t j=0;
           rc = fscanf(f, "%1023s %u", buffer, &j);
           if ((rc != 2) || (strcmp(buffer, "dims_$group_dset$") != 0) || (j!=i)) {
-            FREE(buffer);
-            fclose(f);
-            /* Set pointer to the struct so that the garbage collector can do the job on file handle */
-            file->$group$ = $group$;
-            rc_free = trexio_text_free_$group$(file);
-            assert(rc_free == TREXIO_SUCCESS);
+            trexio_text_free_read_$group$(buffer, f, file, $group$);
             return NULL;
           }
 
           rc = fscanf(f, "%" SCNu64 "\n", &($group$->dims_$group_dset$[i]));
           assert(!(rc != 1));
           if (rc != 1) {
-            FREE(buffer);
-            fclose(f);
-            /* Set pointer to the struct so that the garbage collector can do the job on file handle */
-            file->$group$ = $group$;
-            rc_free = trexio_text_free_$group$(file);
-            assert(rc_free == TREXIO_SUCCESS);
+            trexio_text_free_read_$group$(buffer, f, file, $group$);
             return NULL;
           }
 
@@ -379,24 +369,14 @@ trexio_text_read_$group$ (trexio_text_t* const file)
         /* Allocate arrays */
         $group$->$group_dset$ = CALLOC(size_$group_dset$, $group_dset_dtype$);
         if ($group$->$group_dset$ == NULL) {
-          FREE(buffer);
-          fclose(f);
-          /* Set pointer to the struct so that the garbage collector can do the job on file handle */
-          file->$group$ = $group$;
-          rc_free = trexio_text_free_$group$(file);
-          assert(rc_free == TREXIO_SUCCESS);
+          trexio_text_free_read_$group$(buffer, f, file, $group$);
           return NULL;
         }
 
         for (uint64_t i=0 ; i<size_$group_dset$ ; ++i) {
           rc = fscanf(f, "%$group_dset_format_scanf$", &($group$->$group_dset$[i]));
           if (rc != 1) {
-            FREE(buffer);
-            fclose(f);
-            /* Set pointer to the struct so that the garbage collector can do the job on file handle */
-            file->$group$ = $group$;
-            rc_free = trexio_text_free_$group$(file);
-            assert(rc_free == TREXIO_SUCCESS);
+            trexio_text_free_read_$group$(buffer, f, file, $group$);
             return NULL;
           }
         }
@@ -405,39 +385,28 @@ trexio_text_read_$group$ (trexio_text_t* const file)
       // START REPEAT GROUP_DSET_STR
       } else if (strcmp(buffer, "$group_dset$") == 0) {
 
-        if(size_$group_dset$ != 0) {
+        if (size_$group_dset$ != 0) {
           /* Allocate arrays */
           $group$->$group_dset$ = CALLOC(size_$group_dset$, $group_dset_dtype$);
           if ($group$->$group_dset$ == NULL) {
-            FREE(buffer);
-            fclose(f);
-            /* Set pointer to the struct so that the garbage collector can do the job on file handle */
-            file->$group$ = $group$;
-            rc_free = trexio_text_free_$group$(file);
-            assert(rc_free == TREXIO_SUCCESS);
+            trexio_text_free_read_$group$(buffer, f, file, $group$);
             return NULL;
           }
 
           /* WARNING: this tmp array allows to avoid allocation of space for each element of array of string
-             BUT it's size has to be number_of_str*max_len_str where max_len_str is somewhat arbitrary, e.g. 32.
-           ,*/
+           * BUT it's size has to be number_of_str*max_len_str where max_len_str is somewhat arbitrary, e.g. 32.
+           */
           char* tmp_$group_dset$;
           tmp_$group_dset$ = CALLOC(size_$group_dset$*32, char);
 
           for (uint64_t i=0 ; i<size_$group_dset$ ; ++i) {
             $group$->$group_dset$[i] = tmp_$group_dset$;
             /* conventional fcanf with "%s" only return the string before the first space character
-             ,* to read string with spaces use "%[^\n]" possible with space before or after, i.e. " %[^\n]"
-             ,* Q: depending on what ? */
+             * to read string with spaces use "%[^\n]" possible with space before or after, i.e. " %[^\n]"
+             */
             rc = fscanf(f, " %1023[^\n]", tmp_$group_dset$);
-            assert(!(rc != 1));
             if (rc != 1) {
-              FREE(buffer);
-              fclose(f);
-              /* Set pointer to the struct so that the garbage collector can do the job on file handle */
-              file->$group$ = $group$;
-              rc_free = trexio_text_free_$group$(file);
-              assert(rc_free == TREXIO_SUCCESS);
+              trexio_text_free_read_$group$(buffer, f, file, $group$);
               return NULL;
             }
 
@@ -454,41 +423,25 @@ trexio_text_read_$group$ (trexio_text_t* const file)
         /* additional parameter $group_num$_isSet is needed to suppress warning when fscanf into bool variable using %u or %d */
         rc = fscanf(f, "%u", &($group_num$_isSet));
         $group$->$group_num$_isSet = (bool) $group_num$_isSet;
-        assert(!(rc != 1));
         if (rc != 1) {
-          FREE(buffer);
-          fclose(f);
-          /* Set pointer to the struct so that the garbage collector can do the job on file handle */
-          file->$group$ = $group$;
-          rc_free = trexio_text_free_$group$(file);
-          assert(rc_free == TREXIO_SUCCESS);
+          trexio_text_free_read_$group$(buffer, f, file, $group$);
           return NULL;
         }
 
         if ($group$->$group_num$_isSet == true) {
+
           rc = fscanf(f, "%1023s", buffer);
-          assert(!((rc != 1) || (strcmp(buffer, "$group_num$") != 0)));
           if ((rc != 1) || (strcmp(buffer, "$group_num$") != 0)) {
-            FREE(buffer);
-            fclose(f);
-            /* Set pointer to the struct so that the garbage collector can do the job on file handle */
-            file->$group$ = $group$;
-            rc_free = trexio_text_free_$group$(file);
-            assert(rc_free == TREXIO_SUCCESS);
+            trexio_text_free_read_$group$(buffer, f, file, $group$);
             return NULL;
           }
 
           rc = fscanf(f, "%$group_num_format_scanf$", &($group$->$group_num$));
-          assert(!(rc != 1));
           if (rc != 1) {
-            FREE(buffer);
-            fclose(f);
-            /* Set pointer to the struct so that the garbage collector can do the job on file handle */
-            file->$group$ = $group$;
-            rc_free = trexio_text_free_$group$(file);
-            assert(rc_free == TREXIO_SUCCESS);
+            trexio_text_free_read_$group$(buffer, f, file, $group$);
             return NULL;
           }
+
         }
 
       // END REPEAT GROUP_NUM
@@ -496,52 +449,28 @@ trexio_text_read_$group$ (trexio_text_t* const file)
       } else if (strcmp(buffer, "len_$group_str$") == 0) {
 
         rc = fscanf(f, "%" SCNu64 "", &($group$->len_$group_str$));
-        assert(!(rc != 1));
         if (rc != 1) {
-          FREE(buffer);
-          fclose(f);
-          /* Set pointer to the struct so that the garbage collector can do the job on file handle */
-          file->$group$ = $group$;
-          rc_free = trexio_text_free_$group$(file);
-          assert(rc_free == TREXIO_SUCCESS);
+          trexio_text_free_read_$group$(buffer, f, file, $group$);
           return NULL;
         }
 
         rc = fscanf(f, "%1023s", buffer);
-        assert(!((rc != 1) || (strcmp(buffer, "$group_str$") != 0)));
         if ((rc != 1) || (strcmp(buffer, "$group_str$") != 0)) {
-          FREE(buffer);
-          fclose(f);
-          /* Set pointer to the struct so that the garbage collector can do the job on file handle */
-          file->$group$ = $group$;
-          rc_free = trexio_text_free_$group$(file);
-          assert(rc_free == TREXIO_SUCCESS);
+          trexio_text_free_read_$group$(buffer, f, file, $group$);
           return NULL;
         }
 
         if ($group$->len_$group_str$ != 0) {
 
           $group$->$group_str$ = CALLOC($group$->len_$group_str$, char);
-          assert (!($group$->$group_str$ == NULL));
           if ($group$->$group_str$ == NULL) {
-            FREE(buffer);
-            fclose(f);
-            /* Set pointer to the struct so that the garbage collector can do the job on file handle */
-            file->$group$ = $group$;
-            rc_free = trexio_text_free_$group$(file);
-            assert(rc_free == TREXIO_SUCCESS);
+            trexio_text_free_read_$group$(buffer, f, file, $group$);
             return NULL;
           }
 
           rc = fscanf(f, " %1023[^\n]", $group$->$group_str$);
-          assert(!(rc != 1));
           if (rc != 1) {
-            FREE(buffer);
-            fclose(f);
-            /* Set pointer to the struct so that the garbage collector can do the job on file handle */
-            file->$group$ = $group$;
-            rc_free = trexio_text_free_$group$(file);
-            assert(rc_free == TREXIO_SUCCESS);
+            trexio_text_free_read_$group$(buffer, f, file, $group$);
             return NULL;
           }
 
@@ -561,7 +490,6 @@ trexio_text_read_$group$ (trexio_text_t* const file)
 
   file->$group$ = $group$;
   return $group$;
-
 }
    #+end_src
 
@@ -659,7 +587,7 @@ trexio_text_free_$group$ (trexio_text_t* const file)
 
   // START REPEAT GROUP_DSET_STR
   if ($group$->$group_dset$ != NULL) {
-    if($group$->rank_$group_dset$ != 0) FREE ($group$->$group_dset$[0]);
+    if ($group$->rank_$group_dset$ != 0) FREE ($group$->$group_dset$[0]);
     FREE ($group$->$group_dset$);
   }
   // END REPEAT GROUP_DSET_STR
@@ -673,6 +601,25 @@ trexio_text_free_$group$ (trexio_text_t* const file)
 
   return TREXIO_SUCCESS;
 
+}
+    #+end_src
+
+  This function is called upon the non-successful exit from the ~trexio_text_read_group~ function.
+
+    #+begin_src c :tangle free_group_text.c
+trexio_exit_code
+trexio_text_free_read_$group$ (char* buffer, FILE* txt_file, trexio_text_t* trexio_file, $group$_t* $group$)
+{
+  trexio_exit_code rc_free;
+
+  FREE(buffer);
+  fclose(txt_file);
+  /* Set pointer to the struct so that the garbage collector can do the job on file handle */
+  trexio_file->$group$ = $group$;
+  rc_free = trexio_text_free_$group$(trexio_file);
+  assert(rc_free == TREXIO_SUCCESS);
+
+  return TREXIO_SUCCESS;
 }
     #+end_src
 
@@ -1053,8 +1000,7 @@ trexio_exit_code trexio_text_write_$group_dset$(trexio_t* const file,
 
   /* Open the file in "a" (append) mode to guarantee that no truncation happens upon consecutive writes */
   FILE* f = fopen(file_full_path, "a");
-  if(f == NULL) return TREXIO_FILE_ERROR;
-
+  if (f == NULL) return TREXIO_FILE_ERROR;
 
   /* Specify the line length in order to offset properly. For example, for 4-index quantities
      the line_length is 69 because 10 per index + 4 spaces + 24 for floating point value + 1 for the new line char.
@@ -1089,7 +1035,7 @@ trexio_exit_code trexio_text_write_$group_dset$(trexio_t* const file,
     rc = fprintf(f, format_str,
        $group_dset_sparse_indices_printf$,
        ,*(value_sparse + i));
-    if(rc <= 0) {
+    if (rc <= 0) {
       fclose(f);
       return TREXIO_FAILURE;
     }
@@ -1150,7 +1096,7 @@ trexio_exit_code trexio_text_read_$group_dset$(trexio_t* const file,
 
   /* Open the file in "r" (read) mode to guarantee that no truncation happens upon consecutive reads */
   FILE* f = fopen(file_full_path, "r");
-  if(f == NULL) return TREXIO_FILE_ERROR;
+  if (f == NULL) return TREXIO_FILE_ERROR;
 
   /* Specify the line length in order to offset properly. For example, for 4-index quantities
      the line_length is 69 because 10 per index + 4 spaces + 24 for floating point value + 1 for the new line char
@@ -1176,7 +1122,7 @@ trexio_exit_code trexio_text_read_$group_dset$(trexio_t* const file,
 
       memset(buffer, 0, sizeof(buffer));
 
-      if(fgets(buffer, 1023, f) == NULL){
+      if (fgets(buffer, 1023, f) == NULL){
 
         fclose(f);
         ,*eof_read_size = count;
@@ -1187,7 +1133,7 @@ trexio_exit_code trexio_text_read_$group_dset$(trexio_t* const file,
         rc = sscanf(buffer, "$group_dset_format_scanf$",
                     $group_dset_sparse_indices_scanf$,
                     value_sparse + i);
-        if(rc <= 0) {
+        if (rc <= 0) {
           fclose(f);
           return TREXIO_FAILURE;
         }
@@ -1198,7 +1144,7 @@ trexio_exit_code trexio_text_read_$group_dset$(trexio_t* const file,
 
   /* Close the TXT file */
   rc = fclose(f);
-  if(rc != 0) return TREXIO_FILE_ERROR;
+  if (rc != 0) return TREXIO_FILE_ERROR;
 
   return TREXIO_SUCCESS;
 }
@@ -1225,7 +1171,7 @@ trexio_exit_code trexio_text_read_$group_dset$_size(trexio_t* const file, int64_
 
   /* Open the file in "r" (read) mode to guarantee that no truncation happens upon consecutive reads */
   FILE* f = fopen(file_full_path, "r");
-  if(f == NULL) return TREXIO_FILE_ERROR;
+  if (f == NULL) return TREXIO_FILE_ERROR;
 
 
   /* Read the data from the file and check the return code of fprintf to verify that > 0 bytes have been read or reached EOF */
@@ -1246,7 +1192,7 @@ trexio_exit_code trexio_text_read_$group_dset$_size(trexio_t* const file, int64_
 
   /* Close the TXT file */
   rc = fclose(f);
-  if(rc != 0) return TREXIO_FILE_ERROR;
+  if (rc != 0) return TREXIO_FILE_ERROR;
 
   /* Overwrite the value at the input address and return TREXIO_SUCCESS */
   ,*size_max = size_accum;
@@ -1353,7 +1299,7 @@ trexio_exit_code trexio_text_read_determinant_list(trexio_t* const file,
 
   /* Open the file in "r" (read) mode to guarantee that no truncation happens upon consecutive reads */
   FILE* f = fopen(file_full_path, "r");
-  if(f == NULL) return TREXIO_FILE_ERROR;
+  if (f == NULL) return TREXIO_FILE_ERROR;
 
   /* Specify the line length in order to offset properly.
      Each 64-bit integer takes at most 10 slots and requires one space,
@@ -1381,7 +1327,7 @@ trexio_exit_code trexio_text_read_determinant_list(trexio_t* const file,
     accum = 0UL;
     memset(buffer, 0, buf_size);
 
-    if(fgets(buffer, buf_size-1, f) == NULL){
+    if (fgets(buffer, buf_size-1, f) == NULL){
 
       fclose(f);
       ,*eof_read_size = count;
@@ -1394,7 +1340,7 @@ trexio_exit_code trexio_text_read_determinant_list(trexio_t* const file,
     ,*/
       for (uint32_t j=0; j < (uint32_t) dims[1]; ++j) {
         rc = sscanf(buffer+accum, "%10" SCNd64, list + dims[1]*i + j);
-        if(rc <= 0) {
+        if (rc <= 0) {
           fclose(f);
           return TREXIO_FAILURE;
         }
@@ -1407,7 +1353,7 @@ trexio_exit_code trexio_text_read_determinant_list(trexio_t* const file,
 
   /* Close the TXT file */
   rc = fclose(f);
-  if(rc != 0) return TREXIO_FILE_ERROR;
+  if (rc != 0) return TREXIO_FILE_ERROR;
 
   return TREXIO_SUCCESS;
 }
@@ -1443,7 +1389,7 @@ trexio_exit_code trexio_text_read_determinant_coefficient(trexio_t* const file,
 
   /* Open the file in "r" (read) mode to guarantee that no truncation happens upon consecutive reads */
   FILE* f = fopen(file_full_path, "r");
-  if(f == NULL) return TREXIO_FILE_ERROR;
+  if (f == NULL) return TREXIO_FILE_ERROR;
 
   /* Specify the line length in order to offset properly.
      Each double value 24 elements + one newline char.
@@ -1464,7 +1410,7 @@ trexio_exit_code trexio_text_read_determinant_coefficient(trexio_t* const file,
   for (uint64_t i=0UL; i < dims[0]; ++i) {
 
     memset(buffer, 0, buf_size);
-    if(fgets(buffer, buf_size-1, f) == NULL){
+    if (fgets(buffer, buf_size-1, f) == NULL){
 
       fclose(f);
       ,*eof_read_size = count;
@@ -1473,7 +1419,7 @@ trexio_exit_code trexio_text_read_determinant_coefficient(trexio_t* const file,
     } else {
 
       rc = sscanf(buffer, "%lf", coeff + i);
-      if(rc <= 0) {
+      if (rc <= 0) {
         fclose(f);
         return TREXIO_FAILURE;
       }
@@ -1484,7 +1430,7 @@ trexio_exit_code trexio_text_read_determinant_coefficient(trexio_t* const file,
 
   /* Close the TXT file */
   rc = fclose(f);
-  if(rc != 0) return TREXIO_FILE_ERROR;
+  if (rc != 0) return TREXIO_FILE_ERROR;
 
   return TREXIO_SUCCESS;
 }
@@ -1515,7 +1461,7 @@ trexio_text_read_determinant_coefficient_size(trexio_t* const file, int64_t* con
 
   /* Open the file in "r" (read) mode to guarantee that no truncation happens upon consecutive reads */
   FILE* f = fopen(file_full_path, "r");
-  if(f == NULL) return TREXIO_FILE_ERROR;
+  if (f == NULL) return TREXIO_FILE_ERROR;
 
   /* Read the data from the file and check the return code of fprintf to verify that > 0 bytes have been read or reached EOF */
   int rc;
@@ -1535,7 +1481,7 @@ trexio_text_read_determinant_coefficient_size(trexio_t* const file, int64_t* con
 
   /* Close the TXT file */
   rc = fclose(f);
-  if(rc != 0) return TREXIO_FILE_ERROR;
+  if (rc != 0) return TREXIO_FILE_ERROR;
 
   /* Overwrite the value at the input address and return TREXIO_SUCCESS */
   ,*size_max = size_accum;
@@ -1565,7 +1511,7 @@ trexio_exit_code trexio_text_write_determinant_list(trexio_t* const file,
 
   /* Open the file in "a" (append) mode to guarantee that no truncation happens upon consecutive writes */
   FILE* f = fopen(file_full_path, "a");
-  if(f == NULL) return TREXIO_FILE_ERROR;
+  if (f == NULL) return TREXIO_FILE_ERROR;
 
   /* Write the data in the file and check the return code of fprintf to verify that > 0 bytes have been written */
   int rc;
@@ -1574,7 +1520,7 @@ trexio_exit_code trexio_text_write_determinant_list(trexio_t* const file,
     /* The loop below is needed to write a line with int bit fields for alpha and beta electrons */
     for (uint32_t j=0; j < (uint32_t) dims[1]; ++j) {
       rc = fprintf(f, "%10" PRId64 " ", *(list + i*dims[1] + j));
-      if(rc <= 0) {
+      if (rc <= 0) {
         fclose(f);
         return TREXIO_FAILURE;
       }
@@ -1620,14 +1566,14 @@ trexio_exit_code trexio_text_write_determinant_coefficient(trexio_t* const file,
 
   /* Open the file in "a" (append) mode to guarantee that no truncation happens upon consecutive writes */
   FILE* f = fopen(file_full_path, "a");
-  if(f == NULL) return TREXIO_FILE_ERROR;
+  if (f == NULL) return TREXIO_FILE_ERROR;
 
   /* Write the data in the file and check the return code of fprintf to verify that > 0 bytes have been written */
   int rc;
   for (uint64_t i=0UL; i < dims[0]; ++i) {
 
     rc = fprintf(f, "%24.16e\n", *(coeff + i));
-    if(rc <= 0) {
+    if (rc <= 0) {
       fclose(f);
       return TREXIO_FAILURE;
     }