Allow negative numbers in "list" command's last field to mean range f…

…irst+last .. first.

app/cmd_parse.kpeg

@@ -163,6 +163,7 @@ not_space_colons = ( not_space_colon )+:ary { ary.join }
     filename    = dbl_string | not_space_colons
 file_pos_sep    = sp+ | ':'
      integer    = </[0-9]+/> { text.to_i }
+     sinteger    = </[+-]?[0-9]+/> { text.to_i }
  line_number    = integer
 
 vm_offset = '@' integer:int
@@ -229,7 +230,7 @@ breakpoint_stmt = location:loc - if_unless:iu - condition:cond {
 # the command.  Also, "list" with nothing else is
 # handled there as well
 list_special_targets = <'.' | '-'> { text }
-list_stmt = (list_special_targets | location):loc - (integer:int)? {
+list_stmt = (list_special_targets | location):loc - (sinteger:int)? {
   List.new(loc, int)
 }
   | (list_special_targets | location):loc {

app/cmd_parser.rb

@@ -1379,6 +1379,32 @@ def _integer
     return _tmp
   end
 
+  # sinteger = < /[+-]?[0-9]+/ > { text.to_i }
+  def _sinteger
+
+    _save = self.pos
+            while true # sequence
+              _text_start = self.pos
+              _tmp = scan(/\A(?-mix:[+-]?[0-9]+)/)
+              if _tmp
+                text = get_text(_text_start)
+              end
+              unless _tmp
+                self.pos = _save
+                break
+              end
+              @result = begin;            text.to_i ; end
+              _tmp = true
+              unless _tmp
+                self.pos = _save
+              end
+              break
+            end # end sequence
+
+    set_failed_rule :_sinteger unless _tmp
+    return _tmp
+  end
+
   # line_number = integer
   def _line_number
             _tmp = apply(:_integer)
@@ -1790,7 +1816,7 @@ def _list_special_targets
     return _tmp
   end
 
-  # list_stmt = ((list_special_targets | location):loc - integer:int? {   List.new(loc, int) } | (list_special_targets | location):loc {   List.new(loc, nil) })
+  # list_stmt = ((list_special_targets | location):loc - sinteger:int? {   List.new(loc, int) } | (list_special_targets | location):loc {   List.new(loc, nil) })
   def _list_stmt
 
     _save = self.pos
@@ -1821,7 +1847,7 @@ def _list_stmt
                   break
                 end
                 _save3 = self.pos
-                _tmp = apply(:_integer)
+                _tmp = apply(:_sinteger)
                 int = @result
                 unless _tmp
                   _tmp = true
@@ -1912,6 +1938,7 @@ def _list_stmt
   Rules[:_filename] = rule_info("filename", "(dbl_string | not_space_colons)")
   Rules[:_file_pos_sep] = rule_info("file_pos_sep", "(sp+ | \":\")")
   Rules[:_integer] = rule_info("integer", "< /[0-9]+/ > { text.to_i }")
+  Rules[:_sinteger] = rule_info("sinteger", "< /[+-]?[0-9]+/ > { text.to_i }")
   Rules[:_line_number] = rule_info("line_number", "integer")
   Rules[:_vm_offset] = rule_info("vm_offset", "\"@\" integer:int {     Position.new(nil, nil, :offset, int)   }")
   Rules[:_position] = rule_info("position", "(vm_offset | line_number:l {    Position.new(nil, nil, :line, l)  })")
@@ -1921,7 +1948,7 @@ def _list_stmt
   Rules[:_breakpoint_stmt_no_condition] = rule_info("breakpoint_stmt_no_condition", "location:loc {   Breakpoint.new(loc, false, 'true') }")
   Rules[:_breakpoint_stmt] = rule_info("breakpoint_stmt", "(location:loc - if_unless:iu - condition:cond {      Breakpoint.new(loc, iu == 'unless', cond) } | breakpoint_stmt_no_condition)")
   Rules[:_list_special_targets] = rule_info("list_special_targets", "< (\".\" | \"-\") > { text }")
-  Rules[:_list_stmt] = rule_info("list_stmt", "((list_special_targets | location):loc - integer:int? {   List.new(loc, int) } | (list_special_targets | location):loc {   List.new(loc, nil) })")
+  Rules[:_list_stmt] = rule_info("list_stmt", "((list_special_targets | location):loc - sinteger:int? {   List.new(loc, int) } | (list_special_targets | location):loc {   List.new(loc, nil) })")
 end
 if __FILE__ == $0
   # require 'rubygems'; require_relative '../lib/trepanning';

processor/command/list.rb

@@ -41,8 +41,9 @@ class Trepan::Command::ListCommand < Trepan::Command
 If the location form is used with a subsequent parameter, the
 parameter is the starting line number.  When there two numbers are
 given, the last number value is treated as a stopping line unless it
-is less than the start line, in which case it is taken to mean the
-number of lines to list instead.
+is positive and less than the start line. In this case, it is taken to
+mean the number of lines to list instead. If last is negative, we start
+that many lines back from first and list to first.
 
 Wherever a number is expected, it does not need to be a constant --
 just something that evaluates to a positive integer.
@@ -58,6 +59,7 @@ class Trepan::Command::ListCommand < Trepan::Command
 #{NAME} foo.rb  5 6  # list lines 5 and 6 of foo.rb
 #{NAME} foo.rb  5 2  # Same as above, since 2 < 5.
 #{NAME} foo.rb:5 2   # Same as above
+#{NAME} foo.rb 15 -5 # List lines 10..15 of foo
 #{NAME} FileUtils.cp # List lines around the FileUtils.cp function.
 #{NAME} .            # List lines centered from where we currently are stopped
 #{NAME} . 3          # List 3 lines starting from where we currently are stopped

processor/list.rb

@@ -11,7 +11,7 @@ class Trepan
   class CmdProcessor < VirtualCmdProcessor
 
     # If last is less than first, assume last is a count rather than an
-    # end line number.
+    # end line number. If last is negative, range is [first+last..first].
     def adjust_last(first, last)
       last < first ? first + last - 1 : last
     end
@@ -89,6 +89,7 @@ def parse_list_cmd(position_str, listsize, center_correction=0)
         end
       end
       if last
+        first, last = [first + last, first] if last < 0
         last = adjust_last(first, last)
       else
         first = [1, first - center_correction].max