Module:pt-plural

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-- Gets the plural of Portuguese nouns and adjectives.
 
local accented_letters = {'á', 'é', 'í', 'ó', 'ú', 'â', 'ê', 'ô'}
local remove_accent = {['á']='a', ['é']='e', ['í']='i', ['ó']='o', ['ú']='u', ['â']='a', ['ê']='e', ['ô']='o'}
local vowels = {'a', 'e', 'i', 'o', 'u', 'ã', 'á', 'é', 'í', 'ó', 'ê', 'ô', 'ú'}
local export = {}
 
function export.show(frame)
    local args = frame:getParent().args
    return export.get_plural(args[1])
end

-- Returns a singular’s plural if it can be safely guessed, and an empty string
-- otherwise.
function export.get_plural(lemma)
	
	if (has_space_or_hyphen(lemma)) then return nil end
		
	local suf3 = suffix(lemma, 3);
	local pre3 = prefix(lemma, 3);
	local suf2 = suffix(lemma, 2);
	local pre2 = prefix(lemma, 2);
	
	if (suf3 == "ção" or suf3 == "são") then
		return pre2 .. "ões"
	end
	
	if (suf3 == "çaõ") then
		return pre3 .. "çoens"
	end

	
	if (suf2 == "ão") then return nil end
	
	if (suf2 == "il") then
		if (is_accented(pre2)) then
			return pre2 .. "eis"
		else 
			return pre2 .. "is"
		end
	end
	
	if (suf2 == "el") then 
		if (is_accented(pre2)) then 
			return pre2 .. "eis"
		else
			return pre2 .. "éis"
		end
	end
	
	if (suf2 == "ol") then 
		if (is_accented(pre2)) then 
			return pre2 .. "ois"
		else
			return pre2 .. "óis"
		end
	end

	local suf1 = suffix(lemma, 1);
	local pre1 = prefix(lemma, 1);
	
	if (suf1 == "l") then return pre1 .. "is" end
	
	if (suf1 == "m") then return pre1 .. "ns" end
	
	if (suf1 == "r" or suf1 == "z") then return lemma .. "es" end
	
	if (is_vowel(suf1)) then return lemma .. "s" end
	
	if (suf1 == "s") then 
		local penult = mw.ustring.sub(suf2, 1, 1)
		if (is_accented(penult)) then
			return pre2 .. remove_accent[penult] .. "ses"
		else
			local antepenult = mw.ustring.sub(suf3, 1, 1)
			if ((penult == "u" or penult == "i") and not is_accented(pre1) and not is_vowel(antepenult)) then
				return lemma .. "es"
			else
				return lemma
			end
		end
	end
	
	return nil
	
end


function suffix(word, length)
	return mw.ustring.sub(word, mw.ustring.len(word) - length + 1)
end


function prefix(word, suf_length)
	return mw.ustring.sub(word, 1, mw.ustring.len(word) - suf_length)
end

-- returns whether it has ´ or ^
function is_accented(word)
	return word_has_letter(word, accented_letters)
end

function is_vowel(letter)
	return word_has_letter(letter, vowels)
end

function has_space_or_hyphen(word)
	return mw.ustring.find(word, " ") or mw.ustring.find(word, "-")
end

function word_has_letter(word, array)
	for c = 1, table.getn(array) do
		if (mw.ustring.find(word, array[c])) then
			return true
		end
	end
	return false
end
 
return export