Implement sequence map.

* doc/eclat.conf.5: Document sequence maps.
* lib/Makefile.am: Add new files.
* lib/libeclat.h (eclat_map_drv_seq): New extern.
* lib/seqmap.c: New file.
* src/eclat.c: Minor fixes.
* tests/Makefile.am: Add new testcase.
* tests/testsuite.at: Likewise.
* tests/seqmap.at: New file.

1 files changed, 41 insertions, 0 deletions

diff --git a/doc/eclat.conf.5 b/doc/eclat.conf.5
index 2a49f99..a1286ba 100644
--- a/doc/eclat.conf.5
+++ b/doc/eclat.conf.5
@@ -600,6 +600,47 @@ Defines the name of the database file to use.
 If set to \fBtrue\fR this statement instructs the backend to count
 terminating null character as a part of key length.  By default, the null
 character is not counted.
+.SS SEQUENCE MAP
+Maps of this type consult several other
+.B eclat
+maps in sequence, using return value from the previous map as a
+key to the subsequent one.  The map returns the value produced by the
+last map in sequence.
+.sp
+.nf
+    map \fIname\fR {
+        type sequence;
+        key \fItrans\fR;
+        sequence \fImaps\fR;
+    }
+.fi
+.sp
+.TP
+\fBsequence\fR \fImaps\fR
+This statement defines the sequence of maps to query.  Its argument is
+a list of map names.  The maps it references must be declared
+elsewhere in the configuration file (not necessarily before the
+sequence map that references them.
+.PP
+For example:
+.sp
+.nf
+    map InstanceId {
+        type sequence;
+        sequence (keytab, instancetab);
+    }
+.fi
+.sp
+If the sequence consists of a single element, such a map is
+effectively an alias to the map named by that element:
+.sp
+.nf
+    map i {
+        type sequence;
+        sequence InstanceId;
+    }
+.fi
+.sp
 .SS LDAP MAP
 This map uses LDAP database to translate names.  It is defined using
 the following syntax: