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--- language:types2 [2026/06/25 11:00] – [Macros] rajit
+++ language:types2 [2026/06/27 20:05] (current) – [Example user-defined type with macros and methods] rajit
@@ Line 285: / Line 285: @@
 <code act>
-defproc stack (chan(int)? in; chan(int)!out )
+defproc stack (chan(int)? in; chan(int)! out)
 {
   ...
@@ Line 317: / Line 317: @@
 <code act>
-defproc stack (chan(int)? in; chan(int)!out )
+defproc stack (chan(int)? in; chan(int)! out)
 {
   ...
@@ Line 384: / Line 384: @@
 In the linked example, ''fixpoint<a,b>'' corresponds to a fixed-point number with ''a'' integer bits and ''b'' fractional bits following the standard Q(a,b) format.
+==== Example user-defined type with macros and methods ====
+Combining some of these ideas, the following is an example of a user-defined type corresponding to an N-bit signed integer. Only some methods are defined.
+<code act>
+template<pint W>
+deftype signed_int (int<W> x)
+{
+    { W > 1 : "Need sign bit plus one bit at a minumum" };
+    methods {
+        function plus (signed_int<W> s) : signed_int<W>
+        {
+            chp {
+               self.x := x + s.x // 2's complement!
+             }
+         }
+        macro display()
+        {
+            [ x{W-1} = 1 -> log_p("-", (~x+1))
+            [] else -> log_p(x)
+            ]
+         }
+         macro set(int<W> v)
+         {
+              x := v
+          }
+     }
+}
+</code>
+In this scenario, the following CHP adds two numbers, and then displays the result using a ''log'' statement.
+<code act>
+defproc test()
+{
+   signed_int<8> u, v;
+   chp {
+       v.set(1);
+       u.set(-3);
+       v := v + u;
+       log_st("");
+       v.display();
+       log_nl("")
+    }
+}
+</code>
+This should display ''-2'' as a log message when run using ''actsim''.