add code-style for slides

resources/slides_utils.lua

 function tostr(t)
     local str = ""
     for k, v in next, t do
         if #str > 0 then
             str = str .. ", "
         end
         if type(k) == "number" then
             str = str .. "[" .. k .. "] = "
         else
             str = str .. tostring(k) .. " = "
@@ skipping 40 matching lines @@
     for i = 1, #slides do
         pretty_print_slide(slides[i])
     end
     io.write("}\n")
 end
 
 function parse_transition_type(s)
     return s:match("^<%s*transition%s*=%s*(%a+)%s*>$")
 end
 
+function parse_blockstyle_type(s)
+    return s:match("^<%s*blockstyle%s*=%s*(%a+)%s*>$")
+end
+
 function parse_file(file)
     local slides = {}
     local block = {}
 
     for line in file:lines() do
         local s = trim_ws(line)
         if #s == 0 then   -- done with a block
             if #block > 0 then
                 slides[#slides + 1] = block
                 block = {}
             end
         else
             local transition_type = parse_transition_type(s)
+            local blockstyle = parse_blockstyle_type(s)
             if transition_type then
                 block["transition"] = transition_type
+            elseif blockstyle then
+                block["blockstyle"] = blockstyle
             else
-                local n = count_hypens(s)
-                block[#block + 1] = {
-                    indent = n,
-                    text = trim_ws(s:sub(n + 1, -1))
-                }
+                if block.blockstyle == "code" then
+                    block[#block + 1] = { text = line }
+                else
+                    local n = count_hypens(s)
+                    block[#block + 1] = {
+                        indent = n,
+                        text = trim_ws(s:sub(n + 1, -1))
+                    }
+                end
             end
         end
     end
 --    pretty_print_slides(slides)
     return slides
 end