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+-- Pandoc River writer
+-- it takes out all formatting, leaving only a river of text
+-- running down the page: one word per line
+-- vim: fdm=marker
+-- invoke with: pandoc -t river.lua
+
+local function flow(s)
+    return s:gsub("%s+", "\n")
+end
+
+local function nude(s)
+    -- Expand contractions
+    s = s:gsub("'%a+%s", function (x)
+        if x == "'ll" then
+            return " will "
+        elseif x == "'ve" then
+            return " have "
+        elseif x == "'re" then
+            return " are "
+        else
+            return x
+        end
+    end)
+    -- Get rid of quotes around words
+    s = s:gsub('"', ' ')
+    s = s:gsub("%s+'", ' ')
+    s = s:gsub("'%s+", ' ')
+    -- Remove HTML entities
+    s = s:gsub('&.-;', ' ')
+    s = s:gsub('%b<>', ' ')
+    -- Remove end-of-line backslashes
+    s = s:gsub('%s+\\$', ' ')
+    -- Remove dashes (not hyphens)
+    s = s:gsub('%-%-+', ' ')
+    s = s:gsub('%-%s', ' ')
+    -- Remove general punctuation
+    s = s:gsub('[%.!%?:;,%[%]%(%)<>]', ' ')
+    -- Remove extra spaces
+    s = s:gsub('%s+', ' ')
+    return s:lower()
+end
+
+-- This function is called once for the whole document. Parameters:
+-- body is a string, metadata is a table, variables is a table.
+-- One could use some kind of templating
+-- system here; this just gives you a simple standalone HTML file.
+function Doc(body, metadata, variables)
+    local buffer = ""
+    local function add(s)
+        buffer = buffer .. nude(s) .. "\n"
+    end
+    if metadata['title'] then
+        add(metadata['title'])
+    end
+    if metadata['subtitle'] then
+        add(metadata['subtitle'])
+    end
+    -- TODO: epigraph.content, epigraph.attrib, dedication, other metadata?
+    add(body)
+    return flow(buffer)
+end
+
+-- Remove all formatting {{{
+function Note(s)
+    return nude(s)
+end
+
+function Blocksep()
+    return "\n"
+end
+function Emph(s)
+    return nude(s)
+end
+
+function Strong(s)
+    return nude(s)
+end
+
+function Subscript(s)
+    return nude(s)
+end
+
+function Superscript(s)
+    return nude(s)
+end
+
+function SmallCaps(s)
+    return nude(s)
+end
+
+function Strikeout(s)
+    return nude(s)
+end
+
+function Code(s, attr)
+    return nude(s)
+end
+
+function CodeBlock(s, attr)
+    return nude(s)
+end
+
+function InlineMath(s)
+    return nude(s)
+end
+
+function DisplayMath(s)
+    return nude(s)
+end
+
+function Span(s, attr)
+    return nude(s)
+end
+
+function Cite(s)
+    return nude(s)
+end
+
+function Plain(s)
+    return nude(s)
+end
+
+-- Links only include the link text
+function Link(s, src, tit)
+    return nude(s)
+end
+
+-- Images have nothing to give us
+-- (but add a space just in case)
+function Image(s, src, tit)
+    return "\n"
+end
+
+function CaptionedImage(s, src, tit)
+    return "\n"
+end
+
+function Str(s)
+    return nude(s)
+end
+
+function Div(s, attr)
+    return nude(s)
+end
+
+function Space(s)
+    return "\n"
+end
+
+function LineBreak()
+    return "\n"
+end
+
+function Para(s)
+    return nude(s)
+end
+
+function Header(lev, s, attr)
+    return nude(s)
+end
+
+function BlockQuote(s)
+    return nude(s)
+end
+
+function HorizontalRule()
+    return "\n"
+end
+
+function BulletList(items)
+    local buffer = ""
+    for _, item in pairs(items) do
+        buffer = buffer .. nude(item) .. "\n"
+    end
+    return buffer .. "\n"
+end
+
+function OrderedList(items)
+    local buffer = ""
+    for _, item in pairs(items) do
+        buffer = buffer .. nude(item) .. "\n"
+    end
+    return buffer .. "\n"
+end
+
+function DefinitionList(items)
+    local buffer = ""
+    for _, item in pairs(items) do
+        for k, v in pairs(item) do
+            buffer = buffer .. nude(k) .. "\n" .. nude(v) .. "\n"
+        end
+    end
+    return buffer .. "\n"
+end
+
+function Table(caption, aligns, widths, headers, rows)
+    local buffer = ""
+    local function add(s)
+        buffer = buffer .. nude(s) .. "\n"
+    end
+    if caption ~= "" then
+        add(caption)
+    end
+    for _,h in pairs(headers) do
+        add(h)
+    end
+    for _, row in pairs(rows) do
+        for _, cell in pairs(row) do
+            add(cell)
+        end
+    end
+    return buffer
+end
+-- }}}
+
+-- The following code will produce runtime warnings when you haven't defined
+-- all of the functions you need for the custom writer, so it's useful
+-- to include when you're working on a writer.
+local meta = {}
+meta.__index =
+  function(_, key)
+    io.stderr:write(string.format("WARNING: Undefined function '%s'\n",key))
+    return function() return "" end
+  end
+setmetatable(_G, meta)
+