added digital delay line

README.md

@@ -123,6 +123,10 @@ TYPE out[NUM];
 fwd(out, history(another_value));
 ```
 
+### [delay.hh](delay.hh)
+
+A [Digital delay line](https://en.wikipedia.org/wiki/Digital_delay_line) can be used to align signals with different delays - after filtering, for example.
+
 ### [calculus.hh](calculus.hh)
 
 Some [calculus](https://en.wikipedia.org/wiki/Calculus) functions:

delay.hh

@@ -0,0 +1,33 @@
+/*
+Digital delay line
+
+Copyright 2020 Ahmet Inan <inan@aicodix.de>
+*/
+
+#pragma once
+
+namespace DSP {
+
+template <typename TYPE, int NUM>
+class Delay
+{
+	TYPE buf[NUM];
+	int pos;
+public:
+	Delay() : pos(0)
+	{
+		for (int i = 0; i < NUM; ++i)
+			buf[i] = 0;
+	}
+	TYPE operator () (TYPE input)
+	{
+		TYPE tmp = buf[pos];
+		buf[pos] = input;
+		if (++pos >= NUM)
+			pos = 0;
+		return tmp;
+	}
+};
+
+}
+