+
+\f
+
+struct arithmetic_sequence
+{
+ double first;
+ double increment;
+};
+
+static double
+next_arithmetic (const struct ccase *c UNUSED,
+ casenumber n,
+ void *aux)
+{
+ struct arithmetic_sequence *as = aux;
+ return n * as->increment + as->first;
+}
+
+/* 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)
+{
+ struct arithmetic_sequence *as = xzalloc (sizeof *as);
+ as->first = first;
+ as->increment = increment;
+ return casereader_create_append_numeric (subreader, next_arithmetic,
+ as, free);
+}
+