From 91ac3ca2faae3e78cfea7399a42016ce4a7d74b3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marcel=20Fabian=20Kr=C3=BCger?= <tex@2krueger.de>
Date: Mon, 26 Apr 2021 15:23:42 +0200
Subject: [PATCH] Convert mathbin to mathord if used in odd context

---
 luamml-convert.lua | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/luamml-convert.lua b/luamml-convert.lua
index b7f8189..ab83c94 100644
--- a/luamml-convert.lua
+++ b/luamml-convert.lua
@@ -281,12 +281,35 @@ function nodes_to_table(head, cur_style)
   local result = t
   local nonscript
   local core, mn = space_like
+  local no_binop_context, last_noad, last_noad_core = true
   for n, id, sub in node.traverse(head) do
+    if last_noad and ((id == noad_t and noad_sub[sub] == 'punct') or (id == fence_t and fence_sub[sub] ~= 'left')) then
+      last_noad['tex:class'], last_noad_core[0] = nil, 'mi'
+      last_noad_core.stretchy, last_noad_core.mathvariant = nil, #last_noad_core == 1
+                                                             and type(last_noad_core[0]) == 'string'
+                                                             and utf8.len(last_noad_core[0]) == 1
+                                                             and utf8.codepoint(last_noad_core[0]) < -0x10000
+                                                             and 'normal' or nil
+    end
     local new_core, new_mn
     local props = properties[n] props = props and props.mathml_table
     if props then
       t[#t+1], new_core = props, user_provided
     elseif id == noad_t then
+      local substr = noad_sub[sub]
+      if substr == 'bin' then
+        if no_binop_context then
+          sub, substr = 0, 'ord'
+        end
+      end
+      no_binop_context = false
+          or substr == 'bin'
+          or substr == 'opdisplaylimits'
+          or substr == 'oplimits'
+          or substr == 'opnolimits'
+          or substr == 'rel'
+          or substr == 'open'
+          or substr == 'punct'
       local new_n
       new_n, new_core, new_mn = noad_to_table(n, sub, cur_style, mn)
       if new_mn == false then
@@ -294,8 +317,14 @@ function nodes_to_table(head, cur_style)
       else
         t[#t+1] = new_n -- might be nil
       end
+      if substr == 'bin' then
+        last_noad, last_noad_core = new_n, new_core
+      else
+        last_noad, last_noad_core = nil, nil
+      end
     elseif id == accent_t then
       t[#t+1], new_core = accent_to_table(n, sub, cur_style)
+      no_binop_context, last_noad, last_noad_core = false, nil, nil
     elseif id == style_t then
       if sub ~= cur_style then
         if #t == 0 then
@@ -322,10 +351,13 @@ function nodes_to_table(head, cur_style)
                                         or assert(false)], 2*size), space_like
     elseif id == radical_t then
       t[#t+1], new_core = radical_to_table(n, sub, cur_style)
+      no_binop_context, last_noad, last_noad_core = false, nil, nil
     elseif id == fraction_t then
       t[#t+1], new_core = fraction_to_table(n, sub, cur_style)
+      no_binop_context, last_noad, last_noad_core = false, nil, nil
     elseif id == fence_t then
       t[#t+1], new_core = fence_to_table(n, sub, cur_style)
+      no_binop_context, last_noad, last_noad_core = false, nil, nil
     elseif id == kern_t then
       if not nonscript then
         t[#t+1], new_core = space_to_table(n.kern, sub, cur_style)