CAST allowed a definition to be connected with fewer port arguments than port parameters, assuming that the trailing ports remain unconnected externally. HAC forbids this error-prone mismatch, and requires one to pass in blanks in place of all unconnected ports, even trailing ports.
For example, given a defproc (define) inv with three bool (node) ports and external nodes x, y, z, The following table shows what declaration connections are legal:
| declaration | CAST | HAC
|
|---|---|---|
inv x; | valid | valid
|
inv x(); | valid | invalid
|
inv x(x, y, z); | valid | valid
|
inv x(x, y); | valid | invalid
|
inv x(x); | valid | invalid
|
inv x(x, , z); | valid | valid
|
inv x(x, , ); | valid | valid
|
inv x(x, y, ); | valid | valid
|
The three invalid HAC examples are invalid because the definition of inv requires exactly three port arguments, where only fewer were given.
The above examples show a declaration with port connection in one statement. HAC allows declarations and port connections to be decoupled, so the following examples would be legal:
bool i, o;
inv x;
x(i, o);
inv y;
y(i, );
y(, o);
y( , );