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--- intro_example:loops [2020/06/17 03:25] – created prafull
+++ intro_example:loops [2025/08/24 16:48] (current) – [Array, loops and selection] rajit
@@ Line 1: / Line 1: @@
 ====== Array, loops and selection ======
 Complex datapath designs are often designed with array of simpler cells. The following example show how to create array of simple cells and connect them using loop constructs in ACT.
-<code>
+<code act>
 import "adder.act";
@@ Line 15: / Line 17: @@
   ( i : 8 : fa[i](a[i], b[i], c[i], s[i], c[i+1]);)
 }
+</code>
+In this example we assume that ''adder.act'' has a full adder definition with a prototype that looks like this:
+<code act>
+defproc fulladder (bool? a, b, ci; bool! s, co)
+{ ... }
 </code>
@@ Line 21: / Line 29: @@
 Here are different ways of writing the same loop using another variant of signal connection.
-<code>
+<code act>
 (i : 8 : fa[i].a=a[i]; fa[i].b=b[i]; fa[i].ci=c[i]; fa[i].s=s[i]; fa[i].co=fa[i+1].ci; )
 </code>
-<code>
+This version makes all the connections to the ports explicitly using the connection syntax. Since it is common to connect a number of ports to the same circuit in close proximity in the ACT file, the following syntax is also supported.
+<code act>
 (i : 8 : fa[i](.a=a[i], .b=b[i], .ci=c[i], .s=s[i], .co=fa[i+1].ci) )
 </code>
 An instance of this adder is then created in a separate file as:
-<code>
+<code act>
 import “adder8b.act”;
@@ Line 69: / Line 80: @@
 The example below shows how selection statement is used for conditional execution.
-<code>
+<code act>
 import "gates.act";
@@ Line 81: / Line 92: @@
 </code>
-Depending on the value of index ''i'', input ''x0''/''x1'' are assigned to output ''y'' or ''z''. If ''i'' is even, ''x0'' is assigned to ''y'' and ''x1'' is assigned to ''z''. If ''i'' is odd, ''x0'' is assigned to ''z'' and ''x1'' is assigned to ''y''.
+Depending on the value of index ''i'', input ''x0''/''x1'' are connected to output ''y'' or ''z''. If ''i'' is even, ''x0'' is connected to ''y'' and ''x1'' is connected to ''z''. If ''i'' is odd, ''x0'' is connected to ''z'' and ''x1'' is connected to ''y''.
-====== Checking library dependencies ======
+====== General loops ======
-For a hierarchical design with many imported libraries, it could be useful to get dependency information and see if all the libraries are present in the directories where ACT can find them. The command ''adepend'' is used to check dependencies.
+The parenthesis-based syntax is a compact way to describe simple loop-based replication. If a more complex approach is needed, then a generalized while loop syntax is also available. The selection example earlier could also be re-written as follows:
-<code>
+<code act>
-$ adepend adder8b.act
+import "gates.act";
-adder8b.act:  adder.act   gates.act
+defproc select (bool x0[8], x1[8]; bool y[8], z[8])
+{
+    pint i;
+    i = 0;
+    *[ i < 8 -> x0[i] = y[i]; x1[i] = z[i];
+                x0[i+1] = z[i+1]; x1[i+1] = y[i+1];
+                i = i + 2;
+    ]
+}
 </code>
-Here, running adepend on ''adderb8.act'' shows that it depends on the ''adder.act'' and ''gates.act''.