column -d: Spalten löschen

lib/rdb/cmd/relational.rb

@@ -11,9 +11,20 @@ Rdb.register('row', 'Make a new table where rows match logical condition',
 end
 Rdb.alias_for('select', 'row')
 
-Rdb.register('column', 'Display columns of a table in any order', 'column [ Column ... ] < tableorlist') do |args|
+Rdb.register('column', 'Display columns of a table in any order', 'column [ -d ] [ Column ... ] < tableorlist') do |args|
+  drop = args.first == '-d'
+  args.shift if drop
   t = table_in
-  next t.write if args.empty?
+  next t.write if args.empty? && !drop
+  die 'usage: column -d Column ... < tableorlist' if drop && args.empty?
+
+  if drop # keep every column except the named ones
+    gone = args.map { |a| t.index_of(a) }
+    keep = t.head.each_index.reject { |i| gone.include?(i) }
+    die 'column -d would delete every column' if keep.empty?
+
+    next t.with(head: keep.map { |i| t.head[i] }, rows: t.rows.map { |r| keep.map { |i| r[i] } }).write
+  end
 
   idx = args.map { |a| Rdb.column_index(t.head, a) }
   head = args.each_with_index.map { |a, n| idx[n] ? t.head[idx[n]] : a }