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--- intro_example:chp_fifo2 [2025/04/21 23:07] – rajit
+++ intro_example:chp_fifo2 [2025/05/01 10:47] (current) – [Alternate Buffer] rajit
@@ Line 1: / Line 1: @@
 ====== Alternate Buffer ======
-We start with the previous definition of a templated buffer:
+We start with the earlier example of a templated buffer:
 <code act>
@@ Line 46: / Line 46: @@
 }
 </code>
+Another version of this is the following:
+<code act>
+template<pint N>
+defproc buffer (chan?(int) L; chan!(int) R)
+{
+   one_place_buffer b[N];
+   chan(int) ch[N-1];
+   (i : N :
+      [ i = 0 ->    b[i].L = L; b[i].R = ch[i];
+     [] i = N-1 ->  b[i].L = ch[i-1]; b[i].R = R;
+     [] else -> b[i].L = ch[i-1]; b[i].R = ch[i];
+      ]
+   )
+}
+</code>
+===== Using port connections directly  =====
+Instead of using the dot notation to explicitly connect ports, we observe that each set of connections operates on the same instance ''b[i]''. This can be written as follows:
+<code act>
+template<pint N>
+defproc buffer (chan?(int) L; chan!(int) R)
+{
+   one_place_buffer b[N];
+   chan(int) ch[N-1];
+   (i : N :
+      [ i = 0 ->    b[i](L,ch[i]);
+     [] i = N-1 ->  b[i](ch[i-1],R);
+     [] else -> b[i](ch[i-1], ch[i]);
+      ]
+   )
+}
+</code>
+This approach relies on the order of ports being known; if instead it is preferable to connect ports by name, the following syntax is also valid.
+<code act>
+template<pint N>
+defproc buffer (chan?(int) L; chan!(int) R)
+{
+   one_place_buffer b[N];
+   chan(int) ch[N-1];
+   (i : N :
+      [ i = 0 ->    b[i](.L=L, .R=ch[i]);
+     [] i = N-1 ->  b[i](.L=ch[i-1], .R=R);
+     [] else -> b[i](.L=ch[i-1], .R=ch[i]);
+      ]
+   )
+}
+</code>
+===== Dynamic creation of buffer instances =====
+ACT also permits instances to be created one at a time. So rather than declaring a single buffer array of size ''N'', we can create it one segment of the array at a time.
+<code act>
+template<pint N>
+defproc buffer (chan?(int) L; chan!(int) R)
+{
+   chan(int) ch[N-1];
+   (i : N :
+       one_place_buffer b[i..i];
+      [ i = 0 ->    b[i](.L=L, .R=ch[i]);
+     [] i = N-1 ->  b[i](.L=ch[i-1], .R=R);
+     [] else -> b[i](.L=ch[i-1], .R=ch[i]);
+      ]
+   )
+}
+</code>
+Each ''b[i..i]'' slice augments the array ''b''.
+Note that when connecting to ports, you can leave connections dangling and then refer to them later.
+For example, the following avoids using the extra channel array.
+<code act>
+template<pint N>
+defproc buffer (chan?(int) L; chan!(int) R)
+{
+   chan(int) ch[N-1];
+   (i : N :
+       one_place_buffer b[i..i];
+      [ i = 0 ->    b[i](.L=L);
+     [] i = N-1 ->  b[i](.L=b[i-1].R, .R=R);
+     [] else -> b[i](.L=b[i-1].R);
+      ]
+   )
+}
+</code>
+... which may be easier to read as follows:
+<code act>
+template<pint N>
+defproc buffer (chan?(int) L; chan!(int) R)
+{
+   chan(int) ch[N-1];
+   (i : N :
+       one_place_buffer b[i..i];
+      [ i = 0 ->    b[i].L=L;
+     [] i = N-1 ->  b[i](.L=b[i-1].R, .R=R);
+     [] else -> b[i].L=b[i-1].R;
+      ]
+   )
+}
+</code>
+This version is similar to the original version we started with.