Fuller sample custom reader.

data/reader.lua

@@ -1,42 +1,85 @@
 -- A sample custom reader for a very simple markup language.
 -- This parses a document into paragraphs separated by blank lines.
--- This is _{italic} and this is *{boldface}
+-- This is /italic/ and this is *boldface* and this is `code`
--- This is an escaped special character: \_, \*, \{, \}
+-- and `code``with backtick` (doubled `` = ` inside backticks).
+-- This is an escaped special character: \_, \*, \\
 -- == text makes a level-2 heading
 -- That's it!
 
 -- For better performance we put these functions in local variables:
-local P, S, R, Cf, Cc, Ct, V, Cs, Cg, Cb, B =
+local P, S, R, Cf, Cc, Ct, V, Cs, Cg, Cb, B, C, Cmt =
   lpeg.P, lpeg.S, lpeg.R, lpeg.Cf, lpeg.Cc, lpeg.Ct, lpeg.V,
-  lpeg.Cs, lpeg.Cg, lpeg.Cb, lpeg.B
+  lpeg.Cs, lpeg.Cg, lpeg.Cb, lpeg.B, lpeg.C, lpeg.Cmt
+
+--- if item is a table, concatenate it to acc;
+-- otherwise insert it at the end.
+local function add_item(acc, item)
+  if acc == nil then
+    acc = {}
+  end
+  if type(item) == "table" then
+    for i = 1,#item do
+      add_item(acc, item[i])
+    end
+  else
+    acc[#acc + 1] = item
+  end
+  return acc
+end
+
+local function Many1(parser)
+  return Cf(Cc(nil) * parser^1 , add_item)
+end
+
+local function Many(parser)
+  return (Many1(parser) + Cc{})
+end
 
 local whitespacechar = S(" \t\r\n")
-local specialchar = S("_*{}\\")
+local specialchar = S("/*\\`")
-local escapedchar = P"\\" * specialchar
+local wordchar = (1 - (whitespacechar + specialchar))
-         / function (x) return string.sub(x,2) end
-local wordchar = (P(1) - (whitespacechar + specialchar)) + escapedchar
 local spacechar = S(" \t")
 local newline = P"\r"^-1 * P"\n"
-local blanklines = newline * spacechar^0 * newline^1
+local blanklines = newline * (spacechar^0 * newline)^1
 local endline = newline - blanklines
 
+local function BetweenDelims(c, parser, constructor)
+  local starter = P(c) * #(- whitespacechar)
+  local ender = B(1 - whitespacechar) * P(c)
+  return starter * Many(parser - ender) * C(ender^-1) /
+          function(contents, ender)
+            if ender == "" then -- fallback
+              return { pandoc.Str(c) , contents }
+            else
+              return constructor(contents)
+            end
+          end
+end
+
+
 -- Grammar
 G = P{ "Pandoc",
-  Pandoc = blanklines^-1 * Ct(V"Block"^0) / pandoc.Pandoc;
+  Pandoc = Many(V"Block") / pandoc.Pandoc;
-  Block = V"Header" + V"Para";
+  Block = blanklines^0 * (V"Header" + V"Para") ;
-  Para = Ct(V"Inline"^1) * blanklines^-1 / pandoc.Para;
+  Para = Many1(V"Inline") * blanklines^-1 / pandoc.Para;
-  Header = Ct(Cg(P("=")^1 / function(x) return #x end, "length")
+  Header = (P("=")^1 / string.len)
              * spacechar^1
-             * Cg(Ct(V"Inline"^0), "contents")
+             * Many(V"Inline" - (spacechar^0 * P("=")^0 * blanklines))
-             * blanklines^-1) /
+             * spacechar^0
-             function(res) return pandoc.Header(res.length, res.contents) end;
+             * P("=")^0
-  Inline = V"Emph" + V"Str" + V"Space" + V"SoftBreak" + V"Special" ;
+             * blanklines^-1 /
+             function(lev, contents) return pandoc.Header(lev, contents) end;
+  Inline = V"Emph" + V"Strong" + V"Str" + V"Space" + V"SoftBreak" +
+             V"Code" + V"Escaped" + V"Special";
   Str = wordchar^1 / pandoc.Str;
+  Escaped = "\\" * C(specialchar) / function(s) return pandoc.Str(s) end;
   Space = spacechar^1 / pandoc.Space;
   SoftBreak = endline / pandoc.SoftBreak;
-  Emph = Ct(P"_{" * Cg(Ct((V"Inline" - P"}")^1), "contents") * P"}") /
+  Emph = BetweenDelims("/", V"Inline", pandoc.Emph);
-          function(res) return pandoc.Emph(res.contents) end;
+  Strong = BetweenDelims("*", V"Inline", pandoc.Strong);
-  Special = specialchar / pandoc.Str;
+  Code = P"`" * Ct(( (P"``" / "`") + (C(1) - S"`"))^1) * P"`"
+         / table.concat / pandoc.Code;
+  Special = S"`\\" / pandoc.Str;
 }
 
 function Reader(input)