From f982de18eeb9aabb3abb2aeb70c274543f66b315 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marcel=20Fabian=20Kr=C3=BCger?= <tex@2krueger.de>
Date: Fri, 28 May 2021 18:25:25 +0200
Subject: [PATCH] Baby steps towards pdfTeX comptibility

---
 parse_showlists.lua | 84 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100644 parse_showlists.lua

diff --git a/parse_showlists.lua b/parse_showlists.lua
new file mode 100644
index 0000000..7d15f81
--- /dev/null
+++ b/parse_showlists.lua
@@ -0,0 +1,84 @@
+local l = lpeg or require'lpeg'
+local hex_digit = l.R('09', 'af')
+local function hex_to_int(s) return tonumber(s, 16) end
+local tex_char = l.Cg('^^' * (hex_digit * hex_digit / hex_to_int
+                           + l.R'\0\x3F' / function(s) return s:byte() + 0x40  end
+                           + l.R'\x40\x7F' / function(s) return s:byte() - 0x40  end)
+                   + l.P(1) / string.byte)
+
+local scaled = l.R'09'^1 * '.' * l.R'09'^1 / function(s) return (tonumber(s * 0x10000) + .5) // 1 end
+local delimiter_code = '"' * (l.R('09', 'AF')^1 / function(s)
+  local code = tonumber(s, 16)
+  return {id = 'delim',
+    small_fam = (code >> 20) & 0xF,
+    small_char = (code >> 16) & 0xFF,
+    large_fam = (code >> 4) & 0xF,
+    large_char = code & 0xFF,
+  }
+end)
+
+local math_char = l.Ct('\\fam' * l.Cg(l.R'09'^1 / tonumber, 'fam') * ' ' * l.Cg(tex_char, 'char') * l.Cg(l.Cc'math_char', 'id'))
+
+local simple_noad = l.Ct(
+    '\\math' * l.Cg(
+        'ord' * l.Cc(0)
+      + 'op' * l.Cc(1)
+      + 'bin' * l.Cc(4)
+      + 'rel' * l.Cc(5)
+      + 'open' * l.Cc(6)
+      + 'close' * l.Cc(7)
+      + 'punct' * l.Cc(8)
+      + 'inner' * l.Cc(9)
+      , 'subtype') * l.Cg(l.Cc'noad', 'id')
+  + '\\radical' * l.Cg(delimiter_code, 'left') * l.Cg(l.Cc'radical', 'id')
+  + '\\accent' * l.Cg(math_char, 'accent') * l.Cg(l.Cc'accent', 'id')
+  + l.Cg('\\left' * l.Cc(1)
+       + '\\middle' * l.Cc(2)
+       + '\\right' * l.Cc(3), 'subtype') * l.Cg(delimiter_code, 'delim') * l.Cg(l.Cc'fence', 'id')
+  ) * -1
+
+local fraction_noad = l.Ct('\\fraction, thickness ' * l.Cg('= default' * l.Cc(0x40000000) + scaled, 'width')
+                    * l.Cg(', left-delimiter ' * delimiter_code, 'left')^-1 * l.Cg(', right-delimiter ' * delimiter_code, 'right')^-1)
+                    * -1
+
+local parse_list
+local function parse_kernel(lines, i, prefix)
+  local line = lines[i]
+  if not line or line:sub(1, #prefix) ~= prefix then return nil, i end
+  local result = math_char:match(lines[i], #prefix + 1)
+  if result then return result, i+1 end
+  result, i = parse_list(lines, i, prefix)
+  return {list = result, id = 'sub_mlist'}, i
+end
+function parse_list(lines, i, prefix)
+  i = i or 1
+  prefix = prefix or ''
+  local list = {}
+  while true do
+    local line = lines[i]
+    if not line or line:sub(1, #prefix) ~= prefix then break end
+    local simple = simple_noad:match(line, #prefix+1)
+    if simple then
+      simple.nucleus, i = parse_kernel(lines, i + 1, prefix .. '.')
+      simple.sup, i = parse_kernel(lines, i, prefix .. '^')
+      simple.sub, i = parse_kernel(lines, i, prefix .. '_')
+      list[#list + 1] = simple
+    else
+      local fraction = fraction_noad:match(line, #prefix+1)
+      if fraction then
+        fraction.num, i = parse_kernel(lines, i + 1, prefix .. '\\')
+        fraction.denom, i = parse_kernel(lines, i, prefix .. '/')
+        list[#list + 1] = fraction
+      else
+        print('unknown noad ' .. line:sub(#prefix+1))
+        i = i + 1
+      end
+    end
+  end
+  return list, i
+end
+local lines = {}
+for l in io.lines() do
+  lines[#lines + 1] = l ~= '' and l or nil
+end
+print(require'inspect'((parse_list(lines))))