1 files changed, 153 insertions, 72 deletions
diff --git a/applause.lua b/applause.lua
index 10da958..4aa81a7 100644
--- a/applause.lua
+++ b/applause.lua
@@ -61,7 +61,9 @@ Stream.is_a_stream = true
 -- A stream, produces an infinite number of the same value by default
 -- (eternal quietness by default)
 function Stream:tick()
-	while true do coroutine.yield(self.value) end	
+	return function()
+		return self.value
+	end
 end
 
 function Stream:map(fnc)
@@ -79,6 +81,14 @@ function Stream:sqrt()  return self:map(math.sqrt) end
 function Stream:tan()   return self:map(math.tan) end
 function Stream:tanh()  return self:map(math.tanh) end
 
+function Stream:scan(fnc)
+	return ScanStream:new(self, fnc)
+end
+
+function Stream:fold(fnc)
+	return FoldStream:new(self, fnc)
+end
+
 function Stream:sub(i, j)
 	return SubStream:new(self, i, j)
 end
@@ -98,11 +108,12 @@ function Stream:__len()	return self:len() end
 function Stream:__call()
 	if self:len() == math.huge then error("Cannot serialize infinite stream") end
 
-	local co = coroutine.wrap(self.tick)
+	local tick = self:tick()
 	local vector = {}
 
 	while true do
-		local sample = co(self)
+		local sample = tick()
+
 		if not sample then break end
 		table.insert(vector, sample)
 	end
@@ -168,8 +179,11 @@ VectorStream = DeriveClass(Stream, function(self, vector)
 end)
 
 function VectorStream:tick()
-	for _, v in ipairs(self.vector) do
-		coroutine.yield(tonumber(v))
+	local i = 0
+
+	return function()
+		i = i + 1
+		return self.vector[i]
 	end
 end
 
@@ -194,8 +208,22 @@ ConcatStream = DeriveClass(Stream, function(self, ...)
 end)
 
 function ConcatStream:tick()
-	for _, stream in ipairs(self.streams) do
-		stream:tick()		
+	local i = 1
+	local ticks = {}
+
+	for k = 1, #self.streams do
+		ticks[k] = self.streams[k]:tick()
+	end
+
+	return function()
+		while i <= #self.streams do
+			local sample = ticks[i]()
+
+			if sample then return sample end
+
+			-- try next stream
+			i = i + 1
+		end
 	end
 end
 
@@ -226,7 +254,13 @@ IotaStream = DeriveClass(Stream, function(self, v1, v2)
 end)
 
 function IotaStream:tick()
-	for i = self.from, self.to do coroutine.yield(i) end
+	local i = self.from-1
+
+	return function()
+		if i >= self.to then return end
+		i = i + 1
+		return i
+	end
 end
 
 function IotaStream:len()
@@ -252,13 +286,19 @@ SubStream = DeriveClass(Stream, function(self, stream, i, j)
 end)
 
 function SubStream:tick()
-	local co = coroutine.wrap(self.stream.tick)
+	local tick = self.stream:tick()
 
-	-- skip until self.i
-	for _ = 1, self.i - 1 do co(self.stream) end
+	-- OPTIMIZE: Perhaps ask stream to skip the first
+	-- self.i-1 samples
+	for _ = 1, self.i-1 do tick() end
 
-	-- produce samples i to j
-	for _ = self.i, self.j do coroutine.yield(co(self.stream)) end
+	local i = self.i
+
+	return function()
+		if i > self.j then return end
+		i = i + 1
+		return tick()
+	end
 end
 
 function SubStream:len()
@@ -272,15 +312,17 @@ IndexStream = DeriveClass(Stream, function(self, stream, index_stream)
 end)
 
 function IndexStream:tick()
+	local stream_tick = self.stream:tick()
+	local index_tick = self.index_stream:tick()
+
 	local stream_len = self.stream:len()
-	local co = coroutine.wrap(self.stream.tick)
-	local index_co = coroutine.wrap(self.index_stream.tick)
 
 	-- cache of samples generated by stream
 	local cache = {}
 
-	while true do
-		local index_sample = index_co(self.index_stream)
+	return function()
+		local index_sample = index_tick()
+
 		if not index_sample then return end
 
 		if index_sample < 1 or index_sample > stream_len or
@@ -292,14 +334,14 @@ function IndexStream:tick()
 		                                math.ceil(index_sample)
 
 		while #cache < index_ceil do
-			table.insert(cache, co(self.stream))
+			table.insert(cache, stream_tick())
 		end
 
 		-- applies linear interpolation if index_sample is
 		-- not an integer
-		coroutine.yield(cache[index_floor] +
-		                (cache[index_ceil] - cache[index_floor])*
-		                (index_sample - index_floor))
+		return cache[index_floor] +
+		       (cache[index_ceil] - cache[index_floor])*
+		       (index_sample - index_floor)
 	end
 end
 
@@ -319,28 +361,29 @@ AddStream = DeriveClass(Stream, function(self, ...)
 end)
 
 function AddStream:tick()
-	local coroutines = {}
+	local running = true
+	local ticks = {}
 
-	for k, stream in pairs(self.streams) do
-		coroutines[k] = coroutine.create(stream.tick)
+	for i = 1, #self.streams do
+		ticks[i] = self.streams[i]:tick()
 	end
 
-	while true do
+	return function()
+		if not running then return end
+
 		local sum = 0
-		local running = false
-
-		for k = 1, #self.streams do
-			if coroutine.status(coroutines[k]) ~= "dead" then
-				local state, sample = coroutine.resume(coroutines[k], self.streams[k])
-				if not state then error(sample) end
-			
-				running = running or sample
-				sum = sum + (sample or 0)
+
+		running = nil
+		for i = 1, #ticks do
+			local sample = ticks[i]()
+
+			if sample then
+				running = true
+				sum = sum + sample
 			end
 		end
-		if not running then return end
 
-		coroutine.yield(sum)
+		return running and sum
 	end
 end
 
@@ -362,28 +405,29 @@ MulStream = DeriveClass(Stream, function(self, ...)
 end)
 
 function MulStream:tick()
-	local coroutines = {}
+	local running = true
+	local ticks = {}
 
-	for k, stream in pairs(self.streams) do
-		coroutines[k] = coroutine.create(stream.tick)
+	for i = 1, #self.streams do
+		ticks[i] = self.streams[i]:tick()
 	end
 
-	while true do
+	return function()
+		if not running then return end
+
 		local product = 1
-		local running = false
-
-		for k = 1, #self.streams do
-			if coroutine.status(coroutines[k]) ~= "dead" then
-				local state, sample = coroutine.resume(coroutines[k], self.streams[k])
-				if not state then error(sample) end
-			
-				running = running or sample
-				product = product * (sample or 1)
+
+		running = nil
+		for i = 1, #ticks do
+			local sample = ticks[i]()
+
+			if sample then
+				running = true
+				product = product * sample
 			end
 		end
-		if not running then return end
 
-		coroutine.yield(product)
+		return running and product
 	end
 end
 
@@ -403,12 +447,11 @@ MapStream = DeriveClass(Stream, function(self, stream, fnc)
 end)
 
 function MapStream:tick()
-	local co = coroutine.wrap(self.stream.tick)
+	local tick = self.stream:tick()
 
-	while true do
-		local sample = co(self.stream)
-		if not sample then return end
-		coroutine.yield(self.fnc(sample))
+	return function()
+		local sample = tick()
+		return sample and self.fnc(sample)
 	end
 end
 
@@ -416,6 +459,54 @@ function MapStream:len()
 	return self.stream:len()
 end
 
+ScanStream = DeriveClass(Stream, function(self, stream, fnc)
+	self.stream = tostream(stream)
+	self.fnc = fnc
+end)
+
+function ScanStream:tick()
+	local tick = self.stream:tick()
+	local last_sample = nil
+
+	return function()
+		local sample = tick()
+		if not sample then return end
+
+		last_sample = self.fnc(last_sample, sample)
+		return last_sample
+	end
+end
+
+function ScanStream:len()
+	return self.stream:len()
+end
+
+FoldStream = DeriveClass(Stream, function(self, stream, fnc)
+	self.stream = tostream(stream)
+	self.fnc = fnc
+end)
+
+function FoldStream:tick()
+	local tick = self.stream:tick()
+
+	return function()
+		local l, r
+
+		while true do
+			r = tick()
+			if not r then break end
+
+			l = l and self.fnc(l, r) or r
+		end
+
+		return l
+	end
+end
+
+function FoldStream:len()
+	return self.stream:len() > 0 and 1 or 0
+end
+
 -- primitives
 
 function tostream(v)
@@ -436,27 +527,17 @@ samplerate = 44100
 
 -- Time units: Convert between time and sample numbers
 -- These are functions, so we can round the result
-function seconds(x) return math.floor(samplerate*x) end
-function mseconds(x) return seconds(x/1000) end
+-- automatically
+function secs(x) return math.floor(samplerate*x) end
+function msecs(x) return secs(x/1000) end
 
 -- Wave forms
 function SawOsc(freq)
-	local accu = 0
-
-	return MapStream:new(freq, function(x)
-		accu = (accu + x/samplerate) % 1
-		return accu
+	return ScanStream:new(freq, function(accu, f)
+		return ((accu or 0) + f/samplerate) % 1
 	end)
 end
 
 function SinOsc(freq)
-	-- The following mapping is equivalent to but more efficient as:
-	-- return (SawOsc(freq)*(2*math.pi)):sin()
-
-	local accu = 0
-
-	return MapStream:new(freq, function(x)
-		accu = (accu + x/samplerate) % 1
-		return math.sin(accu*2*math.pi)
-	end)
+	return (SawOsc(freq)*(2*math.pi)):sin()
 end