From 777a3b56e2d38eec34fb30dcd2e884995804939f Mon Sep 17 00:00:00 2001
From: wkh <kh.wild@wicom.li>
Date: Sun, 11 Oct 2026 22:51:43 +0200
Subject: [PATCH] =?UTF-8?q?record:=200=20und=201=20=3D=20erste=20Zeile,=20?=
 =?UTF-8?q?negative=20Nummern=20z=C3=A4hlen=20vom=20Ende?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 CHANGELOG.md              |  5 +++--
 lib/rdb/cmd/relational.rb |  6 ++++--
 man/record.man            | 11 +++++++++++
 test/rdb_test.rb          | 19 ++++++++++++-------
 4 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9f72e1c..7edda44 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,8 +7,9 @@ folgen [Semantic Versioning](https://semver.org/lang/de/). Die Version steht in
 
 ## [Unveröffentlicht]
 
-### Behoben
-- `record 0`, `record -1` und `record abc` lieferten Zeilen vom Ende der Tabelle (negativer Index in Ruby). Jetzt ein Fehler; eine Nummer hinter dem Ende gibt weiterhin eine leere Tabelle.
+### Geändert
+- `record`: 0 und 1 sind die erste Zeile, negative Zahlen zählen vom Ende (`-1` letzte, `-2` vorletzte ...). Außerhalb der Tabelle kommt eine leere Tabelle, Text und Dezimalzahlen sind ein Fehler. (Vorher lieferten 0, -1 und Text ungewollt Zeilen vom Ende.)
+
 
 ### Hinzugefügt
 - Steuertabellen 2026 für `tax`: `demo/taxDE2026`, `taxAT2026`, `taxCH2026` (nur Bundessteuer), `taxLI2026` (nur Landessteuer), erzeugt mit `tools/gen_tax_tables.rb`, mit Tests.
diff --git a/lib/rdb/cmd/relational.rb b/lib/rdb/cmd/relational.rb
index b5aa12a..0f571f6 100644
--- a/lib/rdb/cmd/relational.rb
+++ b/lib/rdb/cmd/relational.rb
@@ -72,10 +72,12 @@ end
 
 Rdb.register('record', 'Find and output a record from a table', 'record number < table') do |args|
   die 'usage: record number < table' unless args.size == 1
-  die "'#{args[0]}' is not a record number (1, 2, 3 ...)" unless args[0].match?(/\A\d+\z/) && args[0].to_i.positive?
+  die "'#{args[0]}' is not a record number (1, 2, 3 ... or -1 for the last)" unless args[0].match?(/\A[+-]?\d+\z/)
 
+  # 0 and 1 are the first record; -1 is the last, -2 the one before it ...
   t = table_in
-  row = t.rows[args[0].to_i - 1]
+  n = args[0].to_i
+  row = n.negative? ? (t.rows[n] if -n <= t.rows.size) : t.rows[[n, 1].max - 1]
   t.with(rows: row ? [row] : []).write
 end
 
diff --git a/man/record.man b/man/record.man
index 5591986..104937d 100644
--- a/man/record.man
+++ b/man/record.man
@@ -59,6 +59,17 @@ you see output in the following format:
 .DM
 	Item 1 is rubber gloves
 .DE
+.SH "Record Numbers"
+.I "(Ruby re-creation only.)"
+Records are counted from 1.
+The numbers 0 and 1 both mean the first record.
+A negative number counts from the end:
+.B \-1
+is the last record,
+.B \-2
+the one before it, and so on.
+A number beyond either end gives a table without records.
+Anything that is not a whole number is an error.
 .SH "See Also"
 .B
 row,
diff --git a/test/rdb_test.rb b/test/rdb_test.rb
index 95fdf50..04227b3 100644
--- a/test/rdb_test.rb
+++ b/test/rdb_test.rb
@@ -5,8 +5,18 @@ require 'pty'
 require_relative '../lib/rdb'
 
 class SelectionTest < RdbCase
-  def test_record_rejects_numbers_below_one_and_junk
-    %w[0 -1 abc 2.5].each do |n|
+  def test_record_zero_and_one_are_the_first_and_negatives_count_from_the_end
+    { '0' => '1', '1' => '1', '2' => '3', '3' => '6', '-1' => '6', '-2' => '3', '-3' => '1', '+2' => '3' }.each do |n, item|
+      assert_equal [[item]], data(rdb('record', n, file: 'owners')).map { |r| r.first(1) }, "record #{n}"
+    end
+  end
+
+  def test_record_beyond_either_end_is_an_empty_table
+    %w[4 9 -4 -9].each { |n| assert_equal [], data(rdb('record', n, file: 'owners')), "record #{n}" }
+  end
+
+  def test_record_rejects_junk
+    %w[abc 2.5 1e3].each do |n|
       out, err, st = run3('record', n, stdin: File.read(File.join(@dir, 'owners')))
       refute st.success?, "record #{n} should fail"
       assert_equal '', out
@@ -14,11 +24,6 @@ class SelectionTest < RdbCase
     end
   end
 
-  def test_record_beyond_the_end_is_an_empty_table
-    assert_equal [], data(rdb('record', '9', file: 'owners'))
-    assert_equal [%w[6 cy]], data(rdb('record', '3', file: 'owners'))
-  end
-
   def test_row_numeric_condition
     out = rdb('row', 'Cost > 5', file: 'inventory')
     assert_equal %w[3 6 7], data(out).map(&:first)