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-- 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* and this is `code`
-- 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, 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.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 wordchar = (1 - (whitespacechar + specialchar))
local spacechar = S(" \t")
local newline = P"\r"^-1 * P"\n"
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 = Many(V"Block") / pandoc.Pandoc;
Block = blanklines^0 * (V"Header" + V"Para") ;
Para = Many1(V"Inline") * blanklines^-1 / pandoc.Para;
Header = (P("=")^1 / string.len)
* spacechar^1
* Many(V"Inline" - (spacechar^0 * P("=")^0 * blanklines))
* spacechar^0
* P("=")^0
* 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 = BetweenDelims("/", V"Inline", pandoc.Emph);
Strong = BetweenDelims("*", V"Inline", pandoc.Strong);
Code = P"`" * Ct(( (P"``" / "`") + (C(1) - S"`"))^1) * P"`"
/ table.concat / pandoc.Code;
Special = S"`\\" / pandoc.Str;
}
function Reader(input)
return lpeg.match(G, input)
end
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