fix pb with empty sequence in ps, after simplication of code involving ownership (views)

Author: ldeniau

src/madl_sequence.mad

@@ -52,7 +52,7 @@ local string, table, io =
 
 -- backup original methods and metamethods
 local sequence_mt = getmetatable(sequence)
-local var_get, var_val, raw_get, is_instanceOf in sequence
+local var_get, var_val, is_instanceOf in sequence
 local seq_cpy, var_set = sequence.copy, sequence_mt.__newindex
 
 -- root object ----------------------------------------------------------------o
@@ -133,7 +133,7 @@ end
 -- check shared element
 local function check_shared (seq, idx)
   local elm = seq.__dat[idx]
-  if is_nil(raw_get(elm, 'l')) then return elm.parent end
+  if is_nil(elm:raw_get'l') then return elm.parent end
   seq_error("invalid shared element (l defined)", seq, idx, elm)
 end
 
@@ -644,8 +644,9 @@ end
 local function flatten_sequ (seq, flat, sref)
   local n, idx = seq:raw_len(), 2
   flat[1] = mkstart {at=0}
+
   for i=1,n do
-    local elm = seq:raw_get(i)
+    local elm = seq:var_get(i)
     if not (is_element(elm) or is_rawtable(elm)) then
       seq_error("invalid element detected", seq, i)
     elseif elm.kind == 'bline' or is_rawtable(elm) then
@@ -706,7 +707,7 @@ local function clear_sub (seq, sref)
 end
 
 -- finalize sequence
-local function finish_sequ (seq)
+local function fini_sequ (seq)
   local data = seq.__dat
 
   -- clear memoization
@@ -729,31 +730,33 @@ end
 -- sequence init (build)
 local function init_mm (seq)
   local n = seq:raw_len()
+
+  -- check if sequence needs __dat
+  if n == 0 and is_nil(seq:raw_get'l') then return seq end
+
   local sref = { dir=seq.dir, sdir={} }
   local data = table.new(n+2,8)
 
-  -- disable inheritance
-  -- seq:set_final()
-
   -- flatten subsequences
   flatten_sequ(seq, data, sref)
   seq:clear_array()
 
-  local ne = #data
+  local ne  = #data
   data.eidx = table.new(0,ne)
   data.spos = table.new(ne,0)
   data.upos = table.new(ne,0)
   data.ds   = table.new(ne,0)
   data.algn = table.new(ne,0)
-  seq.__dat, data.ne = data, ne
+  data.ne   = ne
+  seq.__dat = data
 
   -- set minlen to 1e-6 [m] for MAD-X compatibility
   if option.madxenv then seq.minlen = 1e-6 end
 
   build_idx(data)
   build_pos(seq, sref)
   clear_sub(seq, sref)
-  finish_sequ(seq)
+  fini_sequ(seq)
 
   -- publish sequence elements in MADX environment
   if option.madxenv then seq:publish(MADX, true) end
@@ -764,27 +767,30 @@ end
 local function copy_mm (seq, name_)
   assert(not rawequal(seq, sequence), "invalid argument #1 (cannot copy 'sequence')")
   assert(is_sequence(seq)           , "invalid argument #1 (sequence expected)")
-  local cpy  = seq_cpy(seq,name_)
+  local cpy = seq_cpy(seq,name_)
+
+  -- check if copy needs to be further processed
+  if seq:is_view() then return cpy end
+
   local data = seq.__dat
   local ne   = data.ne
-  local cdat = table.new(ne,5)  -- see init_mm
+  local cdat = table.new(ne,8)  -- see init_mm
   cdat.eidx  = table.new(0,ne)
   cdat.spos  = table.new(ne,0)
   cdat.upos  = table.new(ne,0)
   cdat.ds    = table.new(ne,0)
   cdat.algn  = table.new(ne,0)
   cdat.ne    = ne
+  cpy.__dat  = cdat
 
   for i=1,ne do
     cdat[i] = data[i]:copy()
     cdat.spos[i], cdat.upos[i], cdat.ds[i], cdat.algn[i] =
     data.spos[i], data.upos[i], data.ds[i], data.algn[i]
   end
 
-  cpy:raw_set('__dat', cdat)
-
   build_idx(cdat)
-  finish_sequ(cpy)
+  fini_sequ(cpy)
   return cpy
 end
 
@@ -842,6 +848,11 @@ end
 
 -- methods (readonly) ---------------------------------------------------------o
 
+local function is_view (seq)
+  assert(is_sequence(seq), "invalid argument #1 (sequence expected)")
+  return is_nil(seq:raw_get'__dat')
+end
+
 local function index (seq, idx)
   assert(is_sequence(seq), "invalid argument #1 (sequence expected)")
   assert(is_integer (idx), "invalid argument #2 (integer expected)")
@@ -1121,7 +1132,7 @@ local function build_index (seq)
   assert(is_sequence(seq), "invalid argument #1 (sequence expected)")
   local data = seq.__dat
   build_idx (data)
-  finish_sequ(seq)
+  fini_sequ(seq)
   return seq
 end
 
@@ -1416,7 +1427,7 @@ local function share (seq1, seq2)
       end
     end
   end
-  finish_sequ(seq1) finish_sequ(seq2)
+  fini_sequ(seq1) fini_sequ(seq2)
   return elm_r, idx_r
 end
 
@@ -1453,7 +1464,7 @@ local function unique (seq, fmt_)
       if fmt_ then data.eidx[en] = nil end
     end
   end
-  finish_sequ(seq)
+  fini_sequ(seq)
   return seq
 end
 
@@ -1724,6 +1735,9 @@ sequence :set_methods {
   -- duplicate
   copy          = copy_mm,
 
+  -- ownership
+  is_view       = is_view,
+
   -- flags
   save_flags    = save_flags,
   restore_flags = restore_flags,