Module:Harmonic entropy: Difference between revisions

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@@ Line 15: / Line 15: @@
 	prec = u.eval_num_arg(prec, 3)
 	return u._round(1200*u._log(ratio), prec)
+end
+-- return ratio corresponding to an interval written in backslash notation
+-- edf = ed3/2, edo = ed2, edt = ed3
+local equaves =
+{
+  ['f'] = 3/2,
+  ['o'] = 2,
+  ['t'] = 3
+}
+function p.backslash_ratio(frame)
+	local args = getArgs(frame)
+	return p._backslash_ratio(args[1])
+end
+function p._backslash_ratio(input)
+	-- result defaults to 0
+	local result = 0
+	-- "steps" of "size" equal divisions of "equave" (c/d), defaults to 0\12(edo)
+	local steps, size, equave = 0, 12, 2
+	-- edf = ed3/2, edo = ed2, edt = ed3
+	input = string.lower(input)
+	steps, size = input:match("^%s*([0-9]*)\\([0-9]*).-$")
+	if input:match("^[0-9]*\\[0-9]*[%-]?ed[fot]$") then
+		equave = equaves[tostring(input:match("[fot]"))]
+	else
+		equave = u.eval_num_arg(input:match("^.-ed(.-)%s*$"))
+	end
+	result = tonumber(equave)^(tonumber(steps)/tonumber(size))
+	return result
 end
 return p