New function for adding a numbering column to a casereader.

[pspp-builds.git] / src / data / casereader-translator.c

diff --git a/src/data/casereader-translator.c b/src/data/casereader-translator.c
index 28b9c180a18d7b433a8e8e20ae364f41ee8690bd..229dac2e54944c8df81088080c1032330c0cd84e 100644 (file)
--- a/src/data/casereader-translator.c
+++ b/src/data/casereader-translator.c
@@ -1,20 +1,18 @@
-/* PSPP - computes sample statistics.
+/* PSPP - a program for statistical analysis.
    Copyright (C) 2007 Free Software Foundation, Inc.
 
-   This program is free software; you can redistribute it and/or
-   modify it under the terms of the GNU General Public License as
-   published by the Free Software Foundation; either version 2 of the
-   License, or (at your option) any later version.
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
 
-   This program is distributed in the hope that it will be useful, but
-   WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   General Public License for more details.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
-   along with this program; if not, write to the Free Software
-   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
-   02110-1301, USA. */
+   along with this program.  If not, see <http://www.gnu.org/licenses/>. */
 
 #include <config.h>
 
@@ -35,13 +33,12 @@ struct casereader_translator
   {
     struct casereader *subreader; /* Source of input cases. */
 
-    void (*translate) (const struct ccase *input, struct ccase *output,
-                       void *aux);
+    void (*translate) (struct ccase *input, struct ccase *output, void *aux);
     bool (*destroy) (void *aux);
     void *aux;
   };
 
-static struct casereader_class casereader_translator_class;
+static const struct casereader_class casereader_translator_class;
 
 /* Creates and returns a new casereader whose cases are produced
    by reading from SUBREADER and passing through TRANSLATE, which
@@ -58,7 +55,7 @@ static struct casereader_class casereader_translator_class;
 struct casereader *
 casereader_create_translator (struct casereader *subreader,
                               size_t output_value_cnt,
-                              void (*translate) (const struct ccase *input,
+                              void (*translate) (struct ccase *input,
                                                  struct ccase *output,
                                                  void *aux),
                               bool (*destroy) (void *aux),
@@ -106,10 +103,65 @@ casereader_translator_destroy (struct casereader *reader UNUSED, void *ct_)
 }
 
 /* Casereader class for translating casereader. */
-static struct casereader_class casereader_translator_class =
+static const struct casereader_class casereader_translator_class =
   {
     casereader_translator_read,
     casereader_translator_destroy,
     NULL,
     NULL,
   };
+\f
+struct casereader_arithmetic_sequence 
+  {
+    int value_ofs;
+    double first;
+    double increment;
+    casenumber n;
+  };
+
+static void cas_translate (struct ccase *input, struct ccase *output,
+                           void *aux);
+static bool cas_destroy (void *aux);
+
+/* Creates and returns a new casereader whose cases are produced
+   by reading from SUBREADER and appending an additional value,
+   which takes the value FIRST in the first case, FIRST +
+   INCREMENT in the second case, FIRST + INCREMENT * 2 in the
+   third case, and so on.
+
+   After this function is called, SUBREADER must not ever again
+   be referenced directly.  It will be destroyed automatically
+   when the translating casereader is destroyed. */
+struct casereader *
+casereader_create_arithmetic_sequence (struct casereader *subreader,
+                                       double first, double increment)
+{
+  /* This could be implemented with a great deal more efficiency
+     and generality.  However, this implementation is easy. */
+  struct casereader_arithmetic_sequence *cas = xmalloc (sizeof *cas);
+  cas->value_ofs = casereader_get_value_cnt (subreader);
+  cas->first = first;
+  cas->increment = increment;
+  cas->n = 0;
+  return casereader_create_translator (subreader, cas->value_ofs + 1,
+                                       cas_translate, cas_destroy, cas);
+}
+
+static void
+cas_translate (struct ccase *input, struct ccase *output, void *cas_)
+{
+  struct casereader_arithmetic_sequence *cas = cas_;
+  case_nullify (output);
+  case_move (output, input);
+  case_resize (output, cas->value_ofs + 1);
+  case_data_rw_idx (output, cas->value_ofs)->f
+    = cas->first + cas->increment * cas->n++;
+}
+
+static bool
+cas_destroy (void *cas_) 
+{
+  struct casereader_arithmetic_sequence *cas = cas_;
+  free (cas);
+  return true;
+}