| Prev | Next | Start of Chapter | End of Chapter | Contents | Glossary | Index | Comments | (12 out of 13)

• Type and location of connections

• Existence of connectedness

• Connection direction.

• Portname of a connection.

• Connection position.

• Side of a connection.

• Connection style.

To check the connection direction:

connection-direction
(item1, connection1)
-> symbol
Returns input, output, or none to indicate whether connection1 connected to item1 is directed and, if so, whether it is an input or output connection. The connection1 must be connected directly to item1.

If this function returns a direction of none, you cannot specify with direction none in a connection statement. Instead, do not enter any direction statement.

To check the connection portname:

connection-portname
(item1, connection1)
-> symbol
Returns a symbol indicating the portname at which connection1 attaches to item1.

To check the connection position:

connection-position
(item1, connection1)
-> integer
Returns an integer indicating the position along the side of item1 at which the connection1 is attached. The value is relative to the side of the icon. For example, if an icon is 30 workspace units square, here is how the connections at locations 10 and 20 are returned:

To check the connection side:

connection-side
(item1, connection1)
-> symbol
Returns top, bottom, left, or right, indicating the side of item1 to which the connection1 is attached.

To check the connection style:

connection-style
(item1, connection1)
-> symbol
Returns either diagonal or orthogonal as the style of connection1.

• Whether two items are directly connected in any way.

• Whether two items are directly connected in a specified direction.

• Whether two items are connected via specified port(s).

You can constrain the execution of the body of a rule that detects a connection/disconnection event (described under Detecting Connection and Disconnection Events) by making such execution conditional on one of these functions.

To check whether two items are directly connected in any way:

items-are-connected
(item1: class item, item2: class item)
-> truth-value
Returns true if any connection whatsoever directly connects item1 and item2; else false. Example:

To check whether two items are directly connected in a specified direction:

items-are-connected-with-direction
(item1: class item, item2: class item, item1-direction: symbol)
-> truth-value
Returns true if a connection runs from item1 to item2 and has the specified direction relative to item1; else false. Example:

To check whether two items are directly connected at specified ports:

items-are-connected-at-ports
(item1: class item, item2: class item,
portname1: symbol, portname2: symbol)
-> truth-value
Returns true if a connection runs from item1 to item2 and connects to portname1 on item1 and portname2 on item2; else false. To specify that a portname does not matter, specify any. Example:

| Prev | Next | Start of Chapter | End of Chapter | Contents | Glossary | Index | Comments | (12 out of 13)