Module:Rational: Difference between revisions

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@@ Line 753: / Line 753: @@
 	end
 	return c * 1200 / math.log(2)
+end
+-- return prime factorisation of a rational number
+function p.factorisation(a)
+	if type(a) == 'number' then
+		a = p.new(a)
+	end
+	if a.nan then return 'NaN' end
+	if a.inf then
+		local sign = '+'
+		if a.sign < 0 then
+			sign = '-'
+		end
+		return sign .. '∞'
+	end
+	if a.zero then return '0' end
+	local s = ''
+	if a.sign < 0 then
+		s = s .. '-'
+	end
+	local factors = {}
+	for factor, power in pairs(a) do
+		if type(factor) == 'number' then
+			table.insert(factors, factor)
+		end
+	end
+	table.sort(factors)
+	for i, factor in ipairs(factors) do
+		if i > 1 then s = s .. ' × ' end
+		s = s .. factor
+		if a[factor] ~= 1 then
+			s = s .. '<sup>' .. a[factor] .. '</sup>'
+		end
+	end
+	return s
 end