Module:Navseasoncats

This Lua module is used on many pages and changes may be widely noticed. Test changes in the module's /sandbox or /testcases subpages, or in your own module sandbox. Consider discussing changes on the talk page before implementing them.

This module depends on the following other modules:

About

{{Navseasoncats}} is intended to be a minimal-input, near-universal template for navigating most sequential categories.

Type Example category BC(E)? Example output

Season

2001–02 FA Cup

No

1998–99
1999–2000
2000–01
2001–02
2002–03
2003–04
2004–05

TV season

Futurama (season 1) episodes

–

0
0
0
0
0
1
2
3
4
5
6

Office term (regular)

MEPs 2004–2009

No

1989–1994
1994–1999
1999–2004
2004–2009
2009–2014
2014–2019
2019–2024

Office term (irregular) Wales AMs 2003–2007 No

Numerical range

Taxonbars with 30–34 taxon IDs

–

15–19
20–24
25–29
30–34
35–39
40–44
45–49

Decade 1990s in Scotland BC

Year 1999 in Scotland BC(E)

Year (auto-condensed) Candidates in the 2000 US presidential election –

Year (|skip-gaps=yes) Amusement parks opened in 1880 –

Ordinal (temporal) 2nd-century rabbis BC(E)

Ordinal (numeric) 1st Lok Sabha members –

Ordinal (word) First Dynasty of Egypt –

Roman numeral Deputies of Legislature X of the Kingdom of Italy –

Mixed decade 1760s in the Province of Quebec (1763–1791) –

Mixed year 1778 establishments in the Province of Quebec (1763–1791) –

Searching behavior

Most multi-year seasons/office terms/numerical ranges are acceptable, as long as the season duration/term length/range size is <= 10, and the gap between seasons is <= 6. For series exceeding either of these criteria, see/use {{Irregular navseasoncats}}.

The length of each season is automatically determined from the originating category name, up to and including 10 years. MOS:DATERANGE compliance is preferred, but some deviation is allowed and tracked for regular series with seasons > 1 year long. {{Category redirect}}s are followed, and tracked for either MOS contravention (to be corrected) or for navigational aid (no error). The gap size between successive seasons is also automatically determined, up to and including 5 years, and defaults to 0 (e.g. 1995–96 → 1996–97).

Automatically condensed years are supported for presidential categories only (but can be easily expanded as needed), for gaps up to and including 5 years, and defaults to 1. To skip gaps of up to 25 years in any year categories, use |skip-gaps=yes.

Limitations

Numerical limitations & AD/BC/E

Season/office term categories do not work for any years BC, which will be hidden, because no working examples were found.
Decade categories recognize BC, but not BCE, because no working examples were found.
Ordinal & numeral words do not work above the ninety-ninth & ninety-nine, because no working examples were found.

Condensation

Automatically condensed Olympics display is not supported due to peculiarities; use {{Winter Olympics by year category navigation}}, etc., instead.
Automatically condensed years are supported for presidential categories only, due to their consistency; use |skip-gaps=yes as desired elsewhere.

Work-arounds

Base-name changes: create at least 2 logically numbered {{R from category navigation}} (1 forward & 1 backward), to join both related series.
Unaccounted-for name+number conventions: where a fixed number is part of the prefix text, e.g. Chapter 11 bankruptcies, a non-breaking space may force the template to work. See this fix, where {{title year}} skipped over 11 as part of a word rather than a discrete number. (This has been accounted for and is no longer required in this example.)
General: for large, permanent gaps^† between successive categories, use {{Succeeding category}}, {{Preceding category}}, {{Category pair}}, as needed, in addition to {{Navseasoncats}} on both sides, or in the middle, of the gap. Even if {{Navseasoncats}} is isolated, it has the benefit of confirming the absence of nearby categories to the reader or maintainer.
^†Permanent gaps, where there is confirmed to be an absence of data, and not just a current, yet to be filled, gap on Wikipedia.

Related CfDs

Usage

Typical usage

{{Navseasoncats}}

Specify a minimum and/or maximum year to display

{{Navseasoncats|min=-100}}
{{Navseasoncats|min=100 BC}}
{{Navseasoncats|min=1753|max=1810}}
{{Navseasoncats|max=2026}}

To skip gaps in year categories

{{Navseasoncats|skip-gaps=yes}}

To not automatically follow {{Category redirect}}s

{{Navseasoncats|follow-redirects=no}}

Exceptional cases

{{Navseasoncats|cat=2010s albums}} — to behave as if placed on |cat=; consider using {{Category pair}} instead of |cat=

Testing & debugging

To test the output of the template on a particular category name, use the |testcase= parameter, and |testcasegap= if necessary:

{{Navseasoncats |testcase=1770s in the Province of Quebec (1763–1791) |min=1760}} →

1720s
1730s
1740s
1750s
1760s
1770s
1780s
1790s
1800s
1810s
1820s

{{Navseasoncats |testcase=1770s in the Province of Quebec (1763–1791) |max=1970s}} →

1720s
1730s
1740s
1750s
1760s
1770s
1780s
1790s
1800s
1810s
1820s

To see all links produced and/or tested, and what effect each has on their display, use |list-all-links=yes:

{{Navseasoncats |testcase=Nations at the 2013 World Athletics Championships |min=2008 |skip-gaps=yes |list-all-links=yes}} →

Category:Nations at the 2006 World Athletics Championships (2006) (2006)
Category:Nations at the 2007 World Athletics Championships (2007) (2007)
Category:Nations at the 2008 World Athletics Championships (2008)
Category:Nations at the 2008–2009 World Athletics Championships (2008–2009) (tried; not displayed)
Category:Nations at the 2008–09 World Athletics Championships (2008–09) (tried; not displayed)
Category:Nations at the 2009 World Athletics Championships → Category:Nations at the 2009 World Championships in Athletics (2009)
Category:Nations at the 2011 World Athletics Championships → Category:Nations at the 2011 World Championships in Athletics (2011)
Category:Nations at the 2015 World Athletics Championships → Category:Nations at the 2015 World Championships in Athletics (2015)
Category:Nations at the 2017 World Athletics Championships → Category:Nations at the 2017 World Championships in Athletics (2017)
Category:Nations at the 2019 World Athletics Championships (2019)
Category:Nations at the 2020 World Athletics Championships (2020)
Category:Nations at the 2020–2021 World Athletics Championships (2020–2021) (tried; not displayed)
Category:Nations at the 2020–21 World Athletics Championships (2020–21) (tried; not displayed)
Category:Nations at the 2021 World Athletics Championships (2021)
Category:Nations at the 2021–2022 World Athletics Championships (2021–2022) (tried; not displayed)
Category:Nations at the 2021–22 World Athletics Championships (2021–22) (tried; not displayed)

All possible element types are shown above (blue, red/grey, hidden, and redirect), and would otherwise display as:

2006
2007
2008
2009
2011
2013
2015
2017
2019
2020
2021

Tracking categories

Purge this page to update the totals

If the template encounters an issue, it displays an error message and/or places the category into one or more of the following tracking categories:

Maintenance required

Maintenance possible

Module maintenance possible

Tracking only

Related pages

local p = {}

local errors = ''
local nexistingcats = 0
local currtitle = mw.title.getCurrentTitle()
local testcasecolon = ''
local testcases = (currtitle.subpageText == 'testcases')
if    testcases then testcasecolon = ':' end
local navborder = true
local followRs = true
local listall = false
local listofalllinks = {}
local skipgaps = false
local misctrackingcats = {
	'', -- [1] placeholder for [[Category:Navseasoncats using cat parameter]]'
	'', -- [2] placeholder for [[Category:Navseasoncats using testcase parameter]]'
	'', -- [3] placeholder for [[Category:Navseasoncats range not using en dash]]
	'', -- [4] placeholder for [[Category:Navseasoncats range abbreviated]]
	'', -- [5] placeholder for [[Category:Navseasoncats range redirected (base change)]]
	'', -- [6] placeholder for [[Category:Navseasoncats range redirected (MOS)]]
	'', -- [7] placeholder for [[Category:Navseasoncats isolated]]
	'', -- [8] placeholder for [[Category:Navseasoncats default season gap size]]
	'', -- [9] placeholder for [[Category:Navseasoncats decade redirected]]
	'', --[10] placeholder for [[Category:Navseasoncats year redirected]]
	'', --[11] placeholder for [[Category:Navseasoncats roman numeral redirected]]
	'', --[12] placeholder for [[Category:Navseasoncats nordinal redirected]]
	'', --[13] placeholder for [[Category:Navseasoncats wordinal redirected]]
	'', --[14] placeholder for [[Category:Navseasoncats TV season redirected]]
	'', --[15] placeholder for [[Category:Navseasoncats using skip-gaps parameter]]
}
local avoidself =  (currtitle.text ~= 'Navseasoncats' and          --avoid self
					currtitle.text ~= 'Navseasoncats/doc' and      --avoid self
					currtitle.text ~= 'Navseasoncats/sandbox' and  --avoid self
					(currtitle.nsText ~= 'Template' or testcases)) --avoid nested transclusion errors (i.e. {{Infilmdecade}})


--[[==========================================================================]]
--[[                      Utility & category functions                        ]]
--[[==========================================================================]]

--Error message handling
--Also used by {{Navseasoncats with centuries below decade}}.
function p.errorclass( msg )
	return mw.text.tag( 'span', {class='error mw-ext-cite-error'}, '<b>Error!</b> '..string.gsub(msg, '&#', '&amp;#') )
end

--Failure handling
--Also used by {{Navseasoncats with centuries below decade}}.
function p.failedcat( errors, sortkey )
	if avoidself then
		return (errors or '')..'&#42;&#42;&#42;Navseasoncats failed to generate navbox***'..
			   '[['..testcasecolon..'Category:Navseasoncats failed to generate navbox|'..(sortkey or 'O')..']]'
	end
	return ''
end

--Check for nav_*() navigational isolation (not necessarily an error).
--Used by all nav_*().
function isolatedcat()
	if nexistingcats == 0 and avoidself then
		misctrackingcats[7] = '[['..testcasecolon..'Category:Navseasoncats isolated]]'
	end
end

--
--Now unused, in favor of catlinkfollowr().
--
--Similar to {{LinkCatIfExists2}}: make a piped link to a category, if it exists;
--if it doesn't exist, just display the greyed link title without linking.
function catlink( catname, displaytext )
	catname = mw.text.trim(catname or '')
	displaytext = mw.text.trim(displaytext or '')
	local grey = '#888'
	local disp = catname
	if displaytext ~= '' then --use 'displaytext' parameter if present
		disp = mw.ustring.gsub(displaytext, '%s+%(.+$', ''); --strip any trailing disambiguator
	end
	
	local exists = mw.title.new( catname, 'Category' ).exists
	if exists then
		nexistingcats = nexistingcats + 1
		return '[[:Category:'..catname..'|'..disp..']]'
	else
		return '<span style="color:'..grey..'">'..disp..'</span>'
	end
end

--Similar to catlink() but follows {{Category redirect}}s.
--Returns { <#R target navelement>, <basetext of #R target> } if {{Category redirect}} followed;
--returns { <original navelement>, nil } otherwise.
--Used by all nav_*().
function catlinkfollowr( catname, displaytext )
	catname = mw.text.trim(catname or '')
	displaytext = mw.text.trim(displaytext or '')
	local grey = '#888'
	local disp = catname
	if displaytext ~= '' then --use 'displaytext' parameter if present
		disp = mw.ustring.gsub(displaytext, '%s+%(.+$', ''); --strip any trailing disambiguator
	end
	
	local link, nilorR
	local exists = mw.title.new( catname, 'Category' ).exists
	if exists then
		nexistingcats = nexistingcats + 1
		if followRs then
			local R = rtarget(catname)
			if R == catname then --no #R
				link = '[[:Category:'..catname..'|'..disp..']]'
				nilorR = nil
			else --#R followed
				link = '[[:Category:'..R..'|'..disp..']]'
				nilorR = R
			end
		else
			link = '[[:Category:'..catname..'|'..disp..']]'
			nilorR = nil
		end
	else
		link = '<span style="color:'..grey..'">'..disp..'</span>'
		nilorR = nil
		--return { '[[:Category:'..catname..'|'..disp..']]', nil } --for debugging
	end
	
	if listall then
		if nilorR then --#R followed
			table.insert( listofalllinks, '[[:Category:'..catname..']] → '..'[[:Category:'..nilorR..']] ('..link..')' )
		else --no #R
			table.insert( listofalllinks, '[[:Category:'..catname..']] ('..link..')' )
		end
	end
	
	return { link, nilorR }
end

--Returns the target of {{Category redirect}}, if it exists, else returns the original cat.
--Used by catlinkfollowr(), and so indirectly by all nav_*().
function rtarget( cat )
	local catcontent = mw.title.new( cat or '', 'Category' ):getContent()
	if string.match( catcontent or '', '{{ *[Cc]at' ) then
		local regex = {
			--from https://dispenser.info.tm/~dispenser/cgi-bin/rdcheck.py?page=Template:Category_redirect
			--the following 11 pages (7 condensed) redirect to [[Template:Category redirect]] (as of 6/2019):
			{ '1', '{{ *[Cc]ategory *[Rr]edirect' }, --most likely match 1st
			{ '2', '{{ *[Cc]at *redirect' },         --444+240 transclusions
			{ '3', '{{ *[Cc]at *redir' },            --8+3
			{ '4', '{{ *[Cc]ategory *move' },        --6
			{ '5', '{{ *[Cc]at *red' },              --6
			{ '6', '{{ *[Cc]atr' },                  --4
			{ '7', '{{ *[Cc]at *move' },             --0
		}
		for k, v in pairs (regex) do
			local rtarget = mw.ustring.match( catcontent, v[2]..'%s*|%s*([^|}]+)' )
			if rtarget then
				rtarget = mw.ustring.gsub(rtarget, '^1%s*=%s*', '')
				rtarget = string.gsub(rtarget, '^[Cc]ategory:', '')
				return rtarget
			end
		end
	end
	return cat
end

--Returns a numbered list of all {{Category redirect}}s followed by catlinkfollowr() -> rtarget().
--Used by all nav_*().
function listalllinks()
	local nl = '\n# '
	local out = ''
	if currtitle.nsText == 'Category' then
		errors = p.errorclass('The <b><code>|list-followed-redirects=yes</code></b> parameter/utility '..
							'should not be saved in category space, only previewed.')
		out = p.failedcat(errors, 'Z')
	end
	if listofalllinks[1] then
		return out..nl..table.concat(listofalllinks, nl)
	else
		return out..nl..'No links found!?'
	end
end

--Returns an unsigned string of the 1-4 digit decade ending in "0", else error.
--Used by nav_decade() only.
function sterilizedec( decade )
	if decade == nil or decade == '' then
		return nil
	end
	
	local dec = string.match(decade, '^[-%+]?(%d?%d?%d?0)$') or 
				string.match(decade, '^[-%+]?(%d?%d?%d?0)%D')
	if dec then
		return dec
	else
		--fix 2-4 digit decade
		local decade_fixed234 = string.match(decade, '^[-%+]?(%d%d?%d?)%d$') or
								string.match(decade, '^[-%+]?(%d%d?%d?)%d%D')
		if decade_fixed234 then
			return decade_fixed234..'0'
		end
		
		--fix 1-digit decade
		local decade_fixed1   = string.match(decade, '^[-%+]?(%d)$') or
								string.match(decade, '^[-%+]?(%d)%D')
		if decade_fixed1 then
			return '0'
		end
		
		--unfixable
		errors = 'sterilizedec() error'
		return nil
	end
end

--Check for nav_hyphen default gap size + isolatedcat() (not necessarily an error).
--Used by nav_hyphen() only.
function defaultgapcat( bool )
	if bool and nexistingcats == 0 and avoidself then
		--using "nexistingcats > 0" isn't as useful, since the default gap size obviously worked
		misctrackingcats[8] = '[['..testcasecolon..'Category:Navseasoncats default season gap size]]'
	end
end

--12 -> 12th, etc.
--Used by nav_nordinal(), nav_wordinal(), and {{Navseasoncats with centuries below decade}}.
function p.addord( i )
	if tonumber(i) then
		local s = tostring(i)
		
		local tens = string.match(s, '1%d$')
		if    tens then return s..'th' end
		
		local  ones = string.match(s, '%d$')
		if     ones == '1' then return s..'st'
		elseif ones == '2' then return s..'nd'
		elseif ones == '3' then return s..'rd' end
		
		return s..'th'
	end
	return i
end


--[[==========================================================================]]
--[[                  Formerly separated templates/modules                    ]]
--[[==========================================================================]]


--[[==========================={{  nav_hyphen  }}=============================]]

function nav_hyphen( start, hyph, finish, firstpart, lastpart, minseas, maxseas, testgap )
	--Expects a PAGENAME of the form "Some sequential 2015–16 example cat", where 
	--	start     = 2015
	--	hyph      = –
	--	finish    = 16 (sequential years can be abbreviated, but others must be full year, i.e. "2001–2005")
	--	firstpart = Some sequential
	--	lastpart  = example cat
	--	minseas   = 1800 ('min' starting season shown; optional)
	--	maxseas   = 1999 ('max' starting season shown; optional; 1999 will show 1999-00)
	--	testgap   = 0 (testcasegap parameter for easier testing; optional)
	
	--sterilize start
	if string.match(start or '', '^%d%d?%d?%d?$') == nil then --1-4 digits, AD only
		local start_fixed = mw.ustring.match(start or '', '^%s*(%d%d?%d?%d?)%D')
		if start_fixed then
			start = start_fixed
		else
			errors = p.errorclass('Function nav_hyphen can\'t recognize the number "'..(start or '')..'" '..
								'in the first part of the "season" that was passed to it. '..
								'For e.g. "2015–16", "2015" is expected via "|2015|–|16|".')
			return p.failedcat(errors, 'H')
		end
	end
	local nstart = tonumber(start)
	
	--en dash check
	if hyph ~= '–' then
		misctrackingcats[3] = '[['..testcasecolon..'Category:Navseasoncats range not using en dash]]' --nav still processable, but track
	end
	
	--sterilize finish
	if string.match(finish or '', '^%d+$') == nil then
		local finish_fixed = mw.ustring.match(finish or '', '^%s*(%d%d?%d?%d?)%D')
		if finish_fixed then
			finish = finish_fixed
		else
			errors = p.errorclass('Function nav_hyphen can\'t recognize "'..(finish or '')..'" '..
								'in the second part of the "season" that was passed to it. '..
								'For e.g. "2015–16", "16" is expected via "|2015|–|16|".')
			return p.failedcat(errors, 'I')
		end
	else
		if string.len(finish) >= 5 then
			errors = p.errorclass('The second part of the season passed to function nav_hyphen should only be four or fewer digits, not "'..(finish or '')..'". '..
								'See [[MOS:DATERANGE]] for details.')
			return p.failedcat(errors, 'J')
		end
	end
	local nfinish = tonumber(finish)
	
	--sterilize min/max
	local nminseas = tonumber(minseas) or -9999 --same behavior as nav_year
	local nmaxseas = tonumber(maxseas) or  9999 --same behavior as nav_year
	if nminseas > nstart then nminseas = nstart end
	if nmaxseas < nstart then nmaxseas = nstart end
	
	local lspace = ' ' --assume a leading space (most common)
	local tspace = ' ' --assume a trailing space (most common)
	if string.match(firstpart, '%($') then lspace = '' end --DNE for "Madrid city councillors (2007–2011)"-type cats
	if string.match(lastpart,  '^%)') then tspace = '' end --DNE for "Madrid city councillors (2007–2011)"-type cats
	
	--calculate term length/intRAseason size & finishing year
	local t = 1
	while t <= 10 do
		local nish = nstart + t --use switchADBC to flip this sign to work for years BC
		if nish == nfinish or string.match(nish, '%d?%d$') == finish then
			break
		end
		if t == 10 then
			errors = p.errorclass('Function nav_hyphen can\'t determine a reasonable term length for "'..start..hyph..finish..'".')
			return p.failedcat(errors, 'K')
		end
		t = t + 1
	end
	
	--apply MOS:DATERANGE to parent
	local lenstart = string.len(start)
	local lenfinish = string.len(finish)
	if lenstart == 4 then --"2001–"
		if t == 1 then --"2001–02" & "2001–2002" both allowed
			if lenfinish ~= 2 and lenfinish ~= 4 then
				errors = p.errorclass('The second part of the season passed to function nav_hyphen should be two or four digits, not "'..finish..'".')
				return p.failedcat(errors, 'L')
			end
		else --"2001–2005" is required for t > 1; track "2001–05"; anything else = error
			if lenfinish == 2 then
				if avoidself then
					misctrackingcats[4] = '[['..testcasecolon..'Category:Navseasoncats range abbreviated]]'
				end
			elseif lenfinish ~= 4 then
				errors = p.errorclass('The second part of the season passed to function nav_hyphen should be four digits, not "'..finish..'".')
				return p.failedcat(errors, 'M')
			end
		end
		if finish == '00' and avoidself then --full year required regardless of term length
			misctrackingcats[4] = '[['..testcasecolon..'Category:Navseasoncats range abbreviated]]'
		end
	end
	
	--calculate intERseason gap size
	local hgapdefault = 0 --assume & start at the most common case: 2001–02, 2002–03, etc.
	local hgap = hgapdefault
	local hgap_success = false
	while hgap <= 5 do --verify
		local prevseason2 = firstpart..lspace..(nstart-t-hgap)..hyph..string.match(nstart-hgap, '%d?%d$')    ..tspace..lastpart
		local nextseason2 = firstpart..lspace..(nstart+t+hgap)..hyph..string.match(nstart+2*t+hgap, '%d?%d$')..tspace..lastpart
		local prevseason4 = firstpart..lspace..(nstart-t-hgap)..hyph..(nstart-hgap)    ..tspace..lastpart
		local nextseason4 = firstpart..lspace..(nstart+t+hgap)..hyph..(nstart+2*t+hgap)..tspace..lastpart
		if t == 1 then --test abbreviated range first, then full range
			if mw.title.new(prevseason2, 'Category').exists or --use 'or', in case we're at the edge of the cat structure,
			   mw.title.new(nextseason2, 'Category').exists or --or we hit a "–00"/"–2000" situation on one side
			   mw.title.new(prevseason4, 'Category').exists or
			   mw.title.new(nextseason4, 'Category').exists
			then
				hgap_success = true
				break
			end
		elseif t > 1 then --test full range first, then abbreviated range
			if mw.title.new(prevseason4, 'Category').exists or --use 'or', in case we're at the edge of the cat structure,
			   mw.title.new(nextseason4, 'Category').exists or --or we hit a "–00"/"–2000" situation on one side
			   mw.title.new(prevseason2, 'Category').exists or 
			   mw.title.new(nextseason2, 'Category').exists
			then
				hgap_success = true
				break
			end
		end
		hgap = hgap + 1
	end
	if hgap_success == false then
		hgap = tonumber(testgap) or hgapdefault --tracked via defaultgapcat()
	end
	
	--begin navhyphen
	local navh = '{| class="toccolours hlist" style="text-align: center; margin: auto;"\n'..'|\n'
	
	local i = -3
	while i <= 3 do
		local from  = nstart + i*(t+hgap)
		local from2 = string.match(from, '%d?%d$')
		local to  = tostring(from+t)
		local to2 = string.match(to, '%d?%d$')
		local tofinal = to2 --assume t=1 and abbreviated 'to' (the most common case)
		if t > 1 or         --per MOS:DATERANGE (e.g. 1999-2004)
		  (from2 - to2) > 0 --century transition exception (e.g. 1999–2000)
		then
			tofinal = to --default to the MOS-correct format, in case no fallbacks found
		end
		
		--check existance of 4-digit, MOS-correct range, with abbreviation fallback
		if t > 1 and string.len(from) == 4 then --e.g. 1999-2004
			--determine which link exists (full or abbr)
			local full = firstpart..lspace..from..hyph..tofinal..tspace..lastpart
			if not mw.title.new( full, 'Category' ).exists then
				local abbr = firstpart..lspace..from..hyph..to2..tspace..lastpart
				if mw.title.new( abbr, 'Category' ).exists then
					tofinal = to2 --rv to MOS-incorrect format; if full AND abbr DNE, then tofinal is still in its MOS-correct format
				end
			end
		elseif t == 1 then --full-year consecutive ranges are also allowed
			local abbr = firstpart..lspace..from..hyph..tofinal..tspace..lastpart --assume tofinal is in abbr format
			if not mw.title.new( abbr, 'Category' ).exists and tofinal ~= to then
				local full = firstpart..lspace..from..hyph..to..tspace..lastpart
				if mw.title.new( full, 'Category' ).exists then
					tofinal = to --if abbr AND full DNE, then tofinal is still in its abbr format (unless it's a century transition)
				end
			end
		end
		
		--populate navh
		if i ~= 0 then --left/right navh
			local orig = firstpart..lspace..from..hyph..tofinal..tspace..lastpart
			local disp = from..hyph..tofinal
			local catlink = catlinkfollowr(orig, disp)
			
			if catlink[2] and avoidself then --a {{Category redirect}} was followed, figure out why
				local origbase = string.gsub(orig, '%d+[–-]%d+', '')
				local rtarbase = string.gsub(catlink[2], '%d+[–-]%d+', '')
				if origbase ~= rtarbase then
					misctrackingcats[5] = '[['..testcasecolon..'Category:Navseasoncats range redirected (base change)]]'
				else
					misctrackingcats[6] = '[['..testcasecolon..'Category:Navseasoncats range redirected (MOS)]]'
				end
			end
			
			if from >= 0 and nminseas <= from and from <= nmaxseas then
				navh = navh..'*'..catlink[1]..'\n'
			else
				local hidden = '<span style="visibility:hidden">'..disp..'</span>'
				navh = navh..'*'..hidden..'\n'
				if listall then
					listofalllinks[#listofalllinks] = listofalllinks[#listofalllinks]..' ('..hidden..')'
				end
			end
		else --center navh
			navh = navh..'*<b>'..start..hyph..finish..'</b>\n'
		end
		
		i = i + 1
	end
	
	isolatedcat()
	defaultgapcat(not hgap_success)
	if listall then
		return listalllinks()
	else
		return navh..'|}'
	end
end


--[[=========================={{  nav_tvseason  }}============================]]

function nav_tvseason( firstpart, tv, lastpart, maximumtv )
	--Expects a PAGENAME of the form "Futurama (season 1) episodes", where 
	--	firstpart = Futurama (season 
	--	tv        = 1
	--	lastpart  = ) episodes
	--	maximumtv = 7 ('max' tv season parameter; optional)
	tv = tonumber(tv)
	if tv == nil then
		errors = p.errorclass('Function nav_tvseason can\'t recognize the TV season number sent to its 2nd parameter.')
		return p.failedcat(errors, 'T')
	end
	
	local maxtv = tonumber(maximumtv) or 9999 --allow +/- qualifier
	if maxtv < tv then maxtv = tv end --input error; maxtv should be >= parent
	
	local loffset = 0 --left-offset
	--if tv <= 5 then loffset = 6 - tv end --commented to behave similarly to the other nav_* functions
	
	--begin navtvseason
	local navt = '{| class="toccolours hlist" style="text-align: center; margin: auto;"\n'..'|\n'
	
	local i = (-5 + loffset)
	while i <= (5 + loffset) do
		local t = tv + i
		if i ~= 0 then --left/right navt
			local catlink = catlinkfollowr( firstpart..' '..t..lastpart, t )
			if (t >= 1 and t <= maxtv) then --hardcode mintv
				if catlink[2] and avoidself then --a {{Category redirect}} was followed
					misctrackingcats[14] = '[['..testcasecolon..'Category:Navseasoncats TV season redirected]]'
				end
				navt = navt..'*'..catlink[1]..'\n'
			else
				local hidden = '<span style="visibility:hidden">'..'0'..'</span>' --'0' to maintain dot spacing
				navt = navt..'*'..hidden..'\n'
				if listall then
					listofalllinks[#listofalllinks] = listofalllinks[#listofalllinks]..' ('..hidden..')'
				end
			end
		else --center navt
			navt = navt..'*<b>'..tv..'</b>\n'
		end
		
		i = i + 1
	end
	
	isolatedcat()
	if listall then
		return listalllinks()
	else
		return navt..'|}'
	end
end


--[[==========================={{  nav_decade  }}=============================]]

function nav_decade( firstpart, decade, lastpart, mindecade, maxdecade )
	--Expects a PAGENAME of the form "Some sequential 2000 example cat", where 
	--	firstpart = Some sequential
	--	decade    = 2000
	--	lastpart  = example cat
	--	mindecade = 1800 ('min' decade parameter; optional)
	--	maxdecade = 2020 ('max' decade parameter; optional; defaults to next decade)
	
	--sterilize dec
	local dec = sterilizedec(decade)
	if errors ~= '' then
		errors = p.errorclass('Function nav_decade was sent "'..(decade or '')..'" as its 2nd parameter, '..
							'but expects a 1 to 4-digit year ending in "0".')
		return p.failedcat(errors, 'D')
	end
	local ndec = tonumber(dec)
	
	--sterilize mindecade & determine AD/BC
	local mindefault = '-9999'
	local mindec = sterilizedec(mindecade) --returns a tostring(unsigned int), or nil + errors
	if mindec then
		if string.match(mindecade, '-%d') or 
		   string.match(mindecade, 'BC')
		then
			mindec = '-'..mindec --better +/-0 behavior with strings (0-initialized int == "-0" string...)
		end
	elseif errors ~= '' then
		errors = p.errorclass('Function nav_decade was sent "'..(mindecade or '')..'" as its 4th parameter, '..
							'but expects a 1 to 4-digit year ending in "0", the earliest decade to be shown.')
		return p.failedcat(errors, 'E')
	else
		mindec = mindefault --tonumber() later, after error checks
	end
	
	--sterilize maxdecade & determine AD/BC
	local maxdefault = '9999'
	local maxdec = sterilizedec(maxdecade) --returns a tostring(unsigned int), or nil + error
	if maxdec then
		if string.match(maxdecade, '-%d') or 
		   string.match(maxdecade, 'BC')
		then                     --better +/-0 behavior with strings (0-initialized int == "-0" string...),
			maxdec = '-'..maxdec --but a "-0" string -> tonumber() -> tostring() = "-0",
		end                      --and a  "0" string -> tonumber() -> tostring() =  "0"
	elseif errors ~= '' then
		errors = p.errorclass('Function nav_decade was sent "'..(maxdecade or '')..'" as its 5th parameter, '..
							'but expects a 1 to 4-digit year ending in "0", the highest decade to be shown.')
		return p.failedcat(errors, 'F')
	else
		maxdec = maxdefault
	end
	
	local tspace = ' ' --assume trailing space for "1950s in X"-type cats
	if string.match(lastpart, '^-') then tspace = '' end --DNE for "1970s-related"-type cats
	
	--AD/BC switches & vars
	
	local parentBC = string.match(lastpart, '^BC') --following the "0s BC" convention for all years BC
	lastpart = mw.ustring.gsub(lastpart, '^BC%s*', '') --handle BC separately; AD never used
	--TODO?: handle BCE, but only if it exists in the wild
	
	local dec0to40AD = (ndec >= 0 and ndec <= 40 and not parentBC) --special behavior in this range
	local switchADBC = 1                 --  1=AD parent
	if parentBC then switchADBC = -1 end -- -1=BC parent; possibly adjusted later
	local BCdisp = ''
	local D = -math.huge --secondary switch & iterator for AD/BC transition
	
	--check non-default min/max more carefully; determine right-offset
	local roffset = 0
	if mindec ~= mindefault then
		if tonumber(mindec) > ndec*switchADBC then
			mindec = tostring(ndec*switchADBC) --input error; mindec should be <= parent
		end
	end
	if maxdec ~= maxdefault then --a non-default max will override offsetting behavior
		if tonumber(maxdec) < ndec*switchADBC then
			maxdec = tostring(ndec*switchADBC) --input error; maxdec should be >= parent
		end
	else                            --offset only if 1) max == maxdefault,
--[[ ** BHG commented out default offsets unless and until there is an expicit consensus for this
     ** perverse behaviour, which disrupts navigation by making the poistion of the page's decade
	 ** jump around erratically as we approcha and then pass the current decade
	 
		local thisyear = mw.getContentLanguage():formatDate( 'Y' )
		local nthisdecade = tonumber(string.match(thisyear, '^%d%d%d')..'0')
		if ndec <= nthisdecade then --and 2) we're not on a future-decade cat (e.g. Works set in the 2100s)
			local diff = nthisdecade - ndec*switchADBC --in 2019: diff=30 for 1980, 0 for 2010, -20 for 2030
			if diff < 0 then diff = 0 end  --always show at least 1 decade ahead for present-decade+ cats
			if diff >= 0 and diff <= 30 then
				roffset = 40 - diff --in 2019: roffset=10 for 1980, 40 for 2010, 40 for 2030
			end
		end
    ** End section commented by BHG
 --]]
	end
	local nmindec = tonumber(mindec) --similar behavior to nav_year & nav_nordinal
	local nmaxdec = tonumber(maxdec) --similar behavior to nav_nordinal
	
	--begin navdecade
	local bnb = '' --border/no border
	if navborder == false then --for embedding in {{Navseasoncats with decades below year}}
		bnb = ' border-style: none; background-color: transparent;'
	end
	local navd = '{| class="toccolours hlist" style="text-align: center; margin: auto;'..bnb..'"\n'..'|\n'
	
	local i = (-50 - roffset)
	while i <= (50 - roffset) do
		local d = ndec + i*switchADBC
		
		if i ~= 0 then --left/right navd
			local BC = ''
			BCdisp = ''
			if dec0to40AD then
				if D < -10 then
					d = math.abs(d + 10) --b/c 2 "0s" decades exist: "0s BC" & "0s" (AD)
					BC = 'BC '
					if d == 0 then
						D = -10 --track 1st d = 0 use (BC)
					end
				elseif D >= -10 then
					D = D + 10 --now iterate from 0s AD
					d = D      --2nd d = 0 use
				end
			elseif parentBC then
				if switchADBC == -1 then --parentBC looking at the BC side (the common case)
					BC = 'BC '
					if d == 0 then     --prepare to switch to the AD side on the next iteration
						switchADBC = 1 --1st d = 0 use (BC)
						D = -10        --prep
					end
				elseif switchADBC == 1 then --switched to the AD side
					D = D + 10 --now iterate from 0s AD
					d = D      --2nd d = 0 use (on first use)
				end
			end
			if BC ~= '' and ndec <= 50 then
				BCdisp = ' BC' --show BC for all BC decades whenever a "0s" is displayed on the nav
			end
			
			--determine target cat
			local disp = d..'s'..BCdisp
			local catlink = catlinkfollowr( firstpart..' '..d..'s'..tspace..BC..lastpart, disp )
			if catlink[2] and avoidself then --a {{Category redirect}} was followed
				misctrackingcats[9] = '[['..testcasecolon..'Category:Navseasoncats decade redirected]]'
			end
			
			--populate left/right navd
			local shown = '*'..catlink[1]..'\n'
			local hidden = '<span style="visibility:hidden">'..disp..'</span>'
			local dsign = d --use d for display & dsign for logic
			if BC ~= '' then dsign = -dsign end
			if (nmindec <= dsign) and (dsign <= nmaxdec) then
				if dsign == 0 and (nmindec == 0 or nmaxdec == 0) then --distinguish b/w -0 (BC) & 0 (AD)
					--"zoom in" on +/- 0 and turn dsign/min/max temporarily into +/- 1 for easier processing
					local zsign, zmin, zmax = 1, nmindec, nmaxdec
					if BC ~= '' then zsign = -1 end
					if     mindec == '-0' then zmin = -1
					elseif mindec ==  '0' then zmin =  1 end
					if     maxdec == '-0' then zmax = -1
					elseif maxdec ==  '0' then zmax =  1 end
					
					if (zmin <= zsign) and (zsign <= zmax) then
						navd = navd..shown
						hidden = nil
					else
						navd = navd..'*'..hidden..'\n'
					end
				else
					navd = navd..shown --the common case
					hidden = nil
				end
			else
				navd = navd..'*'..hidden..'\n'
			end
			if listall and hidden then
				listofalllinks[#listofalllinks] = listofalllinks[#listofalllinks]..' ('..hidden..')'
			end
			
		else --center navd
			if D >= -10 then
				D = D + 10 --housekeeping b/w left/right sides
			end
			if parentBC then
				BCdisp = ' BC'
				if ndec == 0 then
					switchADBC = 1 --next element will be 0s AD
					D = -10 --for this special case, D is still -inf
				end
			else
				BCdisp = ''
			end
			navd = navd..'*<b>'..dec..'s'..BCdisp..'</b>\n'
		end
		
		i = i + 10
	end
	
	isolatedcat()
	if listall then
		return listalllinks()
	else
		return navd..'|}'
	end
end


--[[============================{{  nav_year  }}==============================]]

function nav_year( firstpart, year, lastpart, minimumyear, maximumyear )
	--Expects a PAGENAME of the form "Some sequential 1760 example cat", where 
	--	firstpart   = Some sequential
	--	year        = 1760
	--	lastpart    = example cat
	--	minimumyear = 1758 ('min' year parameter; optional)
	--	maximumyear = 1800 ('max' year parameter; optional)
	year = tonumber(year) or tonumber(mw.ustring.match(year or '', '^%s*(%d*)'))
	local minyear = tonumber(string.match(minimumyear or '', '-?%d+')) or -9999    --allow +/- qualifier
	local maxyear = tonumber(string.match(maximumyear or '', '-?%d+')) or  9999    --allow +/- qualifier
	if string.match(minimumyear or '', 'BC') then minyear = -math.abs(minyear) end --allow BC qualifier (AD otherwise assumed)
	if string.match(maximumyear or '', 'BC') then maxyear = -math.abs(maxyear) end --allow BC qualifier (AD otherwise assumed)
	
	if year == nil then
		errors = p.errorclass('Function nav_year can\'t recognize the year sent to its 2nd parameter.')
		return p.failedcat(errors, 'Y')
	end
	
	--AD/BC switches & vars
	
	local yearBCElastparts = { --needed for parent = AD 1-5, when the BC/E format is unknown
		--"BCE" removed to match both AD & BCE cats; easier & faster than multiple string.match()s
		['example_Hebrew people_example'] = 'BCE', --example entry format; add to & adjust as needed
	}
	local parentAD = string.match(firstpart, 'AD$')  --following the "AD 1" convention from AD 1 to AD 10
	local parentBC = string.match(lastpart, '^BCE?') --following the "1 BC" convention for all years BC
	firstpart = mw.ustring.gsub(firstpart, '%s*AD$', '') --handle AD/BC separately for easier & faster accounting
	lastpart  = mw.ustring.gsub(lastpart,  '^BCE?%s*', '')
	local BCe = parentBC or yearBCElastparts[lastpart] or 'BC' --"BC" default
	
	local year1to15AD = (year >= 1 and year <= 15 and not parentBC) --special behavior in this range
	local switchADBC = 1                 --  1=AD parent
	if parentBC then switchADBC = -1 end -- -1=BC parent; possibly adjusted later
	local Y = 0 --secondary iterator for AD-on-a-BC-parent
	
	if minyear > year*switchADBC then minyear = year*switchADBC end --input error; minyear should be <= parent
	if maxyear < year*switchADBC then maxyear = year*switchADBC end --input error; maxyear should be >= parent
	
	--determine interyear gap size to condense special category types, if possible
	local ygapdefault = 1 --assume/start at the most common case: 2001, 2002, etc.
	local ygap = ygapdefault
	if string.match(lastpart, 'presidential') then
		local ygap1, ygap2 = ygapdefault, ygapdefault --need to determine previous & next year gaps indepedently
		local ygap1_success, ygap2_success = false, false
		
		local prevseason = nil
		while ygap1 <= 5 do --Czech Republic, Poland, Sri Lanka, etc. have 5-year terms
			prevseason = firstpart..' '..(year-ygap1)..' '..lastpart
			if mw.title.new(prevseason, 'Category').exists then
				ygap1_success = true
				break
			end
			ygap1 = ygap1 + 1
		end
		
		local nextseason = nil
		while ygap2 <= 5 do --Czech Republic, Poland, Sri Lanka, etc. have 5-year terms
			nextseason = firstpart..' '..(year+ygap2)..' '..lastpart
			if mw.title.new(nextseason, 'Category').exists then
				ygap2_success = true
				break
			end
			ygap2 = ygap2 + 1
		end
		
		if ygap1_success and ygap2_success then
			if ygap1 == ygap2 then ygap = ygap1 end
		elseif ygap1_success then  ygap = ygap1
		elseif ygap2_success then  ygap = ygap2
		end
	end
	
	--skip non-existing years, if requested
	local ynogaps = {} --populate with existing years in the range, at most, [year-60, year+60]
	if skipgaps then
		if year > 70 then --add support for AD/BC (<= AD 10) if/when needed
			local yskipped = {} --track skipped y's to avoid double-checking
			local cat, found, Yeary
			
			 --populate nav element queue outwards positively from the parent
			local Year = year --to save/ratchet progression
			local i = 1
			while i <= 5 do
				local y = 1
				while y <= (15 - i) do --'15' in case we get to i=5 and find nothing 10 y out
					found = false
					Yeary = Year + y
					if yskipped[Yeary] == nil then
						yskipped[Yeary] = Yeary
						cat = firstpart..' '..Yeary..' '..lastpart
						found = mw.title.new( cat, 'Category' ).exists
						if found then break end
					end
					y = y + 1
				end
				if found then Year = Yeary
				else          Year = Year + 1 end
				ynogaps[i] =  Year
				i = i + 1
			end
			
			ynogaps[0] = year --the parent
			
			--populate nav element queue outwards negatively from the parent
			Year = year --reset ratchet
			i = -1
			while i >= -5 do
				local y = -1
				while y >= (-15 - i) do --'-15' in case we get to i=-5 and find nothing -10 y out
					found = false
					Yeary = Year + y
					if yskipped[Yeary] == nil then
						yskipped[Yeary] = Yeary
						cat = firstpart..' '..Yeary..' '..lastpart
						found = mw.title.new( cat, 'Category' ).exists
						if found then break end
					end
					y = y - 1
				end
				if found then Year = Yeary
				else          Year = Year - 1 end
				ynogaps[i] =  Year
				i = i - 1
			end
		else
			skipgaps = false --AD/BC not supported
		end
	end
	
	--begin navyears
	local navy = '{| class="toccolours hlist" style="text-align: center; margin: auto;"\n'..'|\n'
	
	local y
	local i = -5
	while i <= 5 do
		if skipgaps then
			y = ynogaps[i]
		else
			y = year + i*ygap*switchADBC
		end
		local BCdisp = ''
		if i ~= 0 then --left/right navy
			
			local AD = ''
			local BC = ''
			if year1to15AD then
				if year >= 11 then --parent = AD 11-15
					if y <= 10 then --prepend AD on y = 1-10 cats only, per existing cats
						AD = 'AD '
					end
					
				elseif year >= 1 then --parent = AD 1-10
					if y <= 0 then
						BC = BCe..' '
						y = math.abs(y - 1) --skip y = 0 (DNE)
					elseif y >= 1 and y <= 10 then --prepend AD on y = 1-10 cats only, per existing cats
						AD = 'AD '
					end
				end
				
			elseif parentBC then
				if switchADBC == -1 then --displayed y is in the BC regime
					if y >= 1 then     --the common case
						BC = BCe..' '   
					elseif y == 0 then --switch from BC to AD regime
						switchADBC = 1
					end
				end
				if switchADBC == 1 then --displayed y is now in the AD regime
					Y = Y + 1 --skip y = 0 (DNE)
					y = Y     --easiest solution: start another iterator for these AD y's displayed on a BC year parent
					AD = 'AD '
				end
			end
			if BC ~= '' and year <= 5 then --only show 'BC' for parent years <= 5: saves room, easier to read,
				BCdisp = ' '..BCe          --and 6 is the first/last nav year that doesn't need a disambiguator;
			end                            --the center/parent year will always show BC, so no need to show it another 10x
			
			--populate left/right navy
			local ysign = y --use y for display & ysign for logic
			local disp = y..BCdisp
			if BC ~= '' then ysign = -ysign end
			local catlink = catlinkfollowr( firstpart..' '..AD..y..' '..BC..lastpart, disp )
			if (minyear <= ysign) and (ysign <= maxyear) then --ex: 1758, 1759, 1761, 1762, 1763, 1764, 1765
				if catlink[2] and avoidself then --a {{Category redirect}} was followed
					misctrackingcats[10] = '[['..testcasecolon..'Category:Navseasoncats year redirected]]'
				end
				navy = navy..'*'..catlink[1]..'\n'
			else --ex: 1755, 1756, 1757
				local hidden = '<span style="visibility:hidden">'..disp..'</span>'
				navy = navy..'*'..hidden..'\n'
				if listall then
					listofalllinks[#listofalllinks] = listofalllinks[#listofalllinks]..' ('..hidden..')'
				end
			end
		else --center navy; ex: 1760
			if parentBC then BCdisp = ' '..BCe end
			navy = navy..'*<b>'..year..BCdisp..'</b>\n'
		end
		
		i = i + 1
	end
	
	isolatedcat()
	if listall then
		return listalllinks()
	else
		return navy..'|}'
	end
end


--[[==========================={{  nav_roman  }}==============================]]

function nav_roman( firstpart, roman, lastpart, minimumrom, maximumrom )
	local toarabic = require('Module:ConvertNumeric').roman_to_numeral
	local toroman  = require('Module:Roman').main
	
	--sterilize/convert rom/num
	local num = tonumber(toarabic(roman))
	local rom = toroman({ [1] = num })
	if num == nil or rom == nil then --out of range or some other error
		errors = p.errorclass('Function nav_roman can\'t recognize one or more of "'..(num or 'nil')..'" & "'..
							(rom or 'nil')..'" in category "'..firstpart..' '..roman..' '..lastpart..'".')
		return p.failedcat(errors, 'R')
	end
	
	--sterilize min/max
	local minrom = tonumber(minimumrom or '') or tonumber(toarabic(minimumrom or ''))
	local maxrom = tonumber(maximumrom or '') or tonumber(toarabic(maximumrom or ''))
	if minrom < 1 then minrom = 1 end    --toarabic() returns -1 on error
	if maxrom < 1 then maxrom = 9999 end --toarabic() returns -1 on error
	if minrom > num then minrom = num end
	if maxrom < num then maxrom = num end
	
	--begin navroman
	local navr = '{| class="toccolours hlist" style="text-align: center; margin: auto;"\n'..'|\n'
	
	local i = -5
	while i <= 5 do
		local n = num + i
		
		if n >= 1 then
			local r = toroman({ [1] = n })
			if i ~= 0 then --left/right navr
				local catlink = catlinkfollowr( firstpart..' '..r..' '..lastpart, r )
				if minrom <= n and n <= maxrom then
					if catlink[2] and avoidself then --a {{Category redirect}} was followed
						misctrackingcats[11] = '[['..testcasecolon..'Category:Navseasoncats roman numeral redirected]]'
					end
					navr = navr..'*'..catlink[1]..'\n'
				else
					local hidden = '<span style="visibility:hidden">'..r..'</span>'
					navr = navr..'*'..hidden..'\n'
					if listall then
						listofalllinks[#listofalllinks] = listofalllinks[#listofalllinks]..' ('..hidden..')'
					end
				end
			else --center navr
				navr = navr..'*<b>'..r..'</b>\n'
			end
		else
			navr = navr..'*<span style="visibility:hidden">'..'I'..'</span>\n'
		end
		
		i = i + 1
	end
	
	isolatedcat()
	if listall then
		return listalllinks()
	else
		return navr..'|}'
	end
end


--[[=========================={{  nav_nordinal  }}============================]]

function nav_nordinal( firstpart, ord, lastpart, minimumord, maximumord )
	local nord = tonumber(ord)
	local minord = tonumber(string.match(minimumord or '', '(-?%d+)[snrt]?[tdh]?')) or -9999 --allow full ord & +/- qualifier
	local maxord = tonumber(string.match(maximumord or '', '(-?%d+)[snrt]?[tdh]?')) or  9999 --allow full ord & +/- qualifier
	if string.match(minimumord or '', 'BC') then minord = -math.abs(minord) end --allow BC qualifier (AD otherwise assumed)
	if string.match(maximumord or '', 'BC') then maxord = -math.abs(maxord) end --allow BC qualifier (AD otherwise assumed)
	
	local temporal = string.match(lastpart, 'century') or
					 string.match(lastpart, 'millennium')
	
	local tspace = ' ' --assume a trailing space after ordinal
	if string.match(lastpart, '^-') then tspace = '' end --DNE for "19th-century"-type cats
	
	--AD/BC switches & vars
	
	local ordBCElastparts = { --needed for parent = AD 1-5, when the BC/E format is unknown
		--lists the lastpart of valid BCE cats
		--"BCE" removed to match both AD & BCE cats; easier & faster than multiple string.match()s
		['-century Hebrew people'] = 'BCE', --WP:CFD/Log/2016 June 21#Category:11th-century BC Hebrew people
		['-century Jews']          = 'BCE', --co-nominated
		['-century Judaism']       = 'BCE', --co-nominated
		['-century rabbis']        = 'BCE', --co-nominated
	}
	local parentBC = mw.ustring.match(lastpart, '%s(BCE?)')       --"1st-century BC" format
	local lastpartNoBC = mw.ustring.gsub(lastpart, '%sBCE?', '')  --easier than splitting lastpart up in 2; AD never used
	local BCe = parentBC or ordBCElastparts[lastpartNoBC] or 'BC' --"BC" default
	
	local switchADBC = 1                 --  1=AD parent
	if parentBC then switchADBC = -1 end -- -1=BC parent; possibly adjusted later
	local O = 0 --secondary iterator for AD-on-a-BC-parent
	
	if not temporal and minord < 1 then minord = 1 end --nothing before "1st parliament", etc.
	if minord > nord*switchADBC then minord = nord*switchADBC end --input error; minord should be <= parent
	if maxord < nord*switchADBC then maxord = nord*switchADBC end --input error; maxord should be >= parent
	
	--determine right-offset, to not show unnecessary future millenia
	local roffset = 0
	if temporal and nord <= 3 then
		if string.match(lastpartNoBC, 'millennium ') and --only offset "1st millennium BC in Egypt" to "3rd-millennium people"-type cats
		   string.match(lastpartNoBC, 'millennium in fiction') == nil and --except these, which extend > 4th millennium
		   maxord == 9999 --only apply if max unspecified
		then
			if not parentBC and nord <= 3 then --1st, 2nd, & 3rd millennium parents
				roffset = nord + 1
			elseif parentBC and nord == 1 then --1st millennium BC only
				roffset = 1
			end
		end
	end
	
	--begin navnordinal
	local bnb = '' --border/no border
	if navborder == false then --for embedding in {{Navseasoncats with centuries below decade}}
		bnb = ' border-style: none; background-color: transparent;'
	end
	local navo = '{| class="toccolours hlist" style="text-align: center; margin: auto;'..bnb..'"\n'..'|\n'
	
	local i = (-5 - roffset)
	while i <= (5 - roffset) do
		local o = nord + i*switchADBC
		local BC = ''
		local BCdisp = ''
		if i ~= 0 then --left/right navo
			
			if parentBC then
				if switchADBC == -1 then --parentBC looking at the BC side
					if o >= 1 then     --the common case
						BC = ' '..BCe
					elseif o == 0 then --switch to the AD side
						BC = ''
						switchADBC = 1
					end
				end
				if switchADBC == 1 then --displayed o is now in the AD regime
					O = O + 1 --skip o = 0 (DNE)
					o = O     --easiest solution: start another iterator for these AD o's displayed on a BC year parent
				end
			elseif o <= 0 then --parentAD looking at BC side
				BC = ' '..BCe
				o = math.abs(o - 1) --skip o = 0 (DNE)
			end
			if BC ~= '' and nord <= 5 then --only show 'BC' for parent ords <= 5: saves room, easier to read,
				BCdisp = ' '..BCe          --and 6 is the first/last nav ord that doesn't need a disambiguator;
			end                            --the center/parent ord will always show BC, so no need to show it another 10x
			
			--populate left/right navo
			local oth = p.addord(o)
			local osign = o --use o for display & osign for logic
			if BC ~= '' then osign = -osign end
			local hidden = '<span style="visibility:hidden">'..oth..'</span>'
			if temporal then --e.g. "3rd-century BC"
				local lastpart = lastpartNoBC --lest we recursively add multiple "BC"s
				if BC ~= '' then
					lastpart = string.gsub(lastpart, temporal, temporal..BC) --replace BC if needed
				end
				local catlink = catlinkfollowr( firstpart..' '..oth..tspace..lastpart, oth..BCdisp )
				if (minord <= osign) and (osign <= maxord) then
					if catlink[2] and avoidself then --a {{Category redirect}} was followed
						misctrackingcats[12] = '[['..testcasecolon..'Category:Navseasoncats nordinal redirected]]'
					end
					navo = navo..'*'..catlink[1]..'\n'
				else
					navo = navo..'*'..hidden..'\n'
					if listall then
						listofalllinks[#listofalllinks] = listofalllinks[#listofalllinks]..' ('..hidden..')'
					end
				end
			elseif BC == '' and minord <= osign and osign <= maxord then --e.g. >= "1st parliament"
				local catlink = catlinkfollowr( firstpart..' '..oth..tspace..lastpart, oth )
				if catlink[2] and avoidself then --a {{Category redirect}} was followed
					misctrackingcats[12] = '[['..testcasecolon..'Category:Navseasoncats nordinal redirected]]'
				end
				navo = navo..'*'..catlink[1]..'\n'
			else --either out-of-range (hide), or non-temporal + BC = something might be wrong (2nd X parliament BC?); handle exceptions if/as they arise
				navo = navo..'*'..hidden..'\n'
			end
		else --center navo
			if parentBC then BC = ' '..BCe end
			navo = navo..'*<b>'..p.addord(o)..BC..'</b>\n'
		end
		
		i = i + 1
	end
	
	isolatedcat()
	if listall then
		return listalllinks()
	else
		return navo..'|}'
	end
end


--[[========================={{  nav_wordinal  }}=============================]]

function nav_wordinal( firstpart, word, lastpart, minimumword, maximumword, frame )
	local eng2ord = require('Module:ConvertNumeric').english_to_ordinal
	local ord2eng = require('Module:ConvertNumeric').numeral_to_english
	local sc = string.match(word, '^%u') --sentence-case check
	local lc = string.lower(word) --operate on/with lc, and restore any sc later
	local nword = eng2ord(lc)
	local case = nil
	if sc then case = 'U' end
	
	--sterilize min/max
	local minword = 1
	local maxword = 99
	if minimumword then
		local num = tonumber(minimumword)
		if num and 0 < num and num < maxword then
			minword = num
		else
			local ord = eng2ord(minimumword)
			if 0 < ord and ord < maxword then
				minword = ord
			end
		end
	end
	if maximumword then
		local num = tonumber(maximumword)
		if num and 0 < num and num < maxword then
			maxword = num
		else
			local ord = eng2ord(maximumword)
			if 0 < ord and ord < maxword then
				maxword = ord
			end
		end
	end
	if minword > nword then minword = nword end
	if maxword < nword then maxword = nword end
	
	--begin navwordinal
	local navw = '{| class="toccolours hlist" style="text-align: center; margin: auto;"\n'..'|\n'
	
	local i = -5
	while i <= 5 do
		local n = nword + i
		
		if n >= 1 then
			local nth = p.addord(n)
			if i ~= 0 then --left/right navw
				local frame_args = frame:newChild{ args = { n, ord = 'on', case = case } } --easier to do this than modify Module:ConvertNumeric
				local w = ord2eng( frame_args )
				local catlink = catlinkfollowr( firstpart..' '..w..' '..lastpart, nth )
				if minword <= n and n <= maxword then
					if catlink[2] and avoidself then --a {{Category redirect}} was followed
						misctrackingcats[13] = '[['..testcasecolon..'Category:Navseasoncats wordinal redirected]]'
					end
					navw = navw..'*'..catlink[1]..'\n'
				else
					local hidden = '<span style="visibility:hidden">'..nth..'</span>'
					navw = navw..'*'..hidden..'\n'
					if listall then
						listofalllinks[#listofalllinks] = listofalllinks[#listofalllinks]..' ('..hidden..')'
					end
				end
			else --center navw
				navw = navw..'*<b>'..nth..'</b>\n'
			end
		else
			navw = navw..'*<span style="visibility:hidden">'..'0th'..'</span>\n'
		end
		
		i = i + 1
	end
	
	isolatedcat()
	if listall then
		return listalllinks()
	else
		return navw..'|}'
	end
end


--[[==========================={{  find_var  }}===============================]]

--Also used by {{Navseasoncats with centuries below decade}}.
function p.find_var( pn )
	--Extracts the variable text (e.g. 2015–16, 3rd, 2000s, III, etc.) from a string
	local pagename = currtitle.baseText
	if pn and pn ~= '' then
		pagename = pn
	end
	
	local cpagename = 'Category:'..pagename --limited-Lua-regex workaround
	
	local d_season = mw.ustring.match(cpagename, ':(%d+s).+%(%d+[–-]%d+%)') --i.e. [[Category:1760s in the Province of Quebec (1763–1791)]]
	
	local y_season = mw.ustring.match(cpagename, ':(%d+) .+%(%d+[–-]%d+%)') --i.e. [[Category:1763 establishments in the Province of Quebec (1763–1791)]]
	
	local season   = mw.ustring.match(cpagename, '[:%s%(](%d+[–-]%d+)[%)%s]') or --split in 2 b/c you can't frontier '$'/eos?
					 mw.ustring.match(cpagename, '[:%s](%d+[–-]%d+)$')
					
	local tvseason = mw.ustring.match(cpagename, 'season (%d+)') or
					 mw.ustring.match(cpagename, 'series (%d+)')
					
	local nordinal = mw.ustring.match(cpagename, '[:%s](%d+[snrt][tdh])[-%s]') or
					 mw.ustring.match(cpagename, '[:%s](%d+[snrt][tdh])$')
					
	local decade   = mw.ustring.match(cpagename, '[:%s](%d+s)[%s-]') or
					 mw.ustring.match(cpagename, '[:%s](%d+s)$')
					
	local year     = mw.ustring.match(cpagename, '[:%s](%d+)%s') or
					 mw.ustring.match(cpagename, '[:%s](%d+)$')
					
	local roman    = mw.ustring.match(cpagename, '%s([IVXLCDM]+)%s')
	
	local found    = d_season or y_season or season or tvseason or 
					 nordinal or decade or year or roman
	
	if found then
		if string.match(found, '%d%d%d%d%d') == nil then
			--return in order of decreasing complexity/least chance for duplication
			if d_season then return { 'decade',   d_season } end
			if y_season then return { 'year',     y_season } end
			if season   then return { 'season',   season   } end
			if tvseason then return { 'tvseason', tvseason } end
			if nordinal then return { 'nordinal', nordinal } end
			if decade   then return { 'decade',   decade   } end
			if year     then return { 'year',     year     } end
			if roman    then return { 'roman',    roman    } end
		end
	else --try word ('zeroth' to 'ninety-ninth' only)
		local eng2ord = require('Module:ConvertNumeric').english_to_ordinal
		local split = mw.text.split(pagename, ' ')
		for i=1, #split do
			if eng2ord(split[i]) > -1 then
				return { 'wordinal', split[i] }
			end
		end
	end
	
	errors = p.errorclass('Function find_var can\'t find the variable text in category "'..pagename..'".')
	return { 'error', p.failedcat(errors, 'V') }
end


--[[==========================================================================]]
--[[                                  Main                                    ]]
--[[==========================================================================]]

function p.navseasoncats( frame )
	local args = frame:getParent().args
	local dby  = args['decade-below-year']    --used by {{Navseasoncats with decades below year}}
	local cbd  = args['century-below-decade'] --used by {{Navseasoncats with centuries below decade}}
	local cat  = args['cat']                  --'testcase' alias for mainspace
	local list = args['list-all-links']       --utility to output all links & followed #Rs instead of a navbar
	local follow = args['follow-redirects']   --default 'yes'
	local testcase    = args['testcase']
	local testcasegap = args['testcasegap']
	local minimum = args['min']
	local maximum = args['max']
	local skip_gaps = args['skip-gaps']
	
	if dby then
		navborder = false
		dby = string.gsub(dby, '&#32;', ' ') --unicodify forced whitespace
	end
	if cbd then
		navborder = false
		cbd = string.gsub(cbd, '&#32;', ' ') --unicodify forced whitespace
	end
	if follow and follow == 'no' then
		followRs = false
	end
	if list and list == 'yes' then
		listall = true
	end
	if skip_gaps and skip_gaps == 'yes' then
		skipgaps = true
		if avoidself then
			misctrackingcats[15] = '[['..testcasecolon..'Category:Navseasoncats using skip-gaps parameter]]'
		end
	end
	
	if currtitle.nsText == 'Category' then
		if cat      then misctrackingcats[1] = '[['..testcasecolon..'Category:Navseasoncats using cat parameter]]' end
		if testcase then misctrackingcats[2] = '[['..testcasecolon..'Category:Navseasoncats using testcase parameter]]' end
	end
	
	local pagename = testcase or cat or dby or cbd or currtitle.baseText
	
	local findvar = p.find_var(pagename)
	if findvar[1] == 'error' then return findvar[2]..table.concat(misctrackingcats) end --basic format error checking in find_var()
	
	local findvar_escaped = string.gsub( findvar[2], '%-', '%%%-')
	local firstpart, lastpart = string.match(pagename, '^(.-)'..findvar_escaped..'(.*)$')
	firstpart = mw.text.trim(firstpart or '')
	lastpart  = mw.text.trim(lastpart or '')
	
	local start = string.match(findvar[2], '^%d+')
	
	--determine the appropriate nav function
	
	if findvar[1] == 'season' then       --e.g. "1–4", "1999–2000", "2001–02", "2001–2002", "2005–2010", etc.
		local hyphen, finish = mw.ustring.match(findvar[2], '%d([–-])(%d+)') --ascii 150 & 45 (ndash & keyboard hyphen); mw req'd
		return nav_hyphen( start, hyphen, finish, firstpart, lastpart, minimum, maximum, testcasegap )..table.concat(misctrackingcats)
		
	elseif findvar[1] == 'tvseason' then --e.g. "1", "15" but preceded with "season" or "series"
		return nav_tvseason( firstpart, start, lastpart, maximum )..table.concat(misctrackingcats) --"minimum" defaults to 1
		
	elseif findvar[1] == 'decade' then   --e.g. "0s", "2010s"
		return nav_decade( firstpart, start, lastpart, minimum, maximum )..table.concat(misctrackingcats)
		
	elseif findvar[1] == 'year' then     --e.g. "500", "2001"
		return nav_year( firstpart, start, lastpart, minimum, maximum )..table.concat(misctrackingcats)
		
	elseif findvar[1] == 'roman' then    --e.g. "I", "XXVIII"
		return nav_roman( firstpart, findvar[2], lastpart, minimum, maximum )..table.concat(misctrackingcats)
		
	elseif findvar[1] == 'nordinal' then --e.g. "4th"
		return nav_nordinal( firstpart, start, lastpart, minimum, maximum )..table.concat(misctrackingcats)
		
	elseif findvar[1] == 'wordinal' then --e.g. "first", "ninety-ninth"
		return nav_wordinal( firstpart, findvar[2], lastpart, minimum, maximum, frame )..table.concat(misctrackingcats)
		
	else                                 --malformed
		errors = p.errorclass('Failed to determine the appropriate nav function from malformed season "'..findvar[2]..'". ')
		return p.failedcat(errors, 'N')..table.concat(misctrackingcats)
	end
end

return p