is open

operator

Return type:: Switch
Returns:: Returns true if the stream has been opened or reopened and not yet closed, and false otherwise. Replacing is with isnt will reverse the results.

Syntax

stream-name indexer? (is | isnt) open

Purpose

You can use is open to determine if a stream variable is open. A stream is open if it has been opened or reopened, but is not yet closed.

The following code opens a stream if it is not already open:

  open my-stream as buffer unless my-stream is open

The following code shows two OmniMark stream state tests that use isnt open:

  document-start
     local stream s
     ...
     open s as buffer when s isnt open
     ... 
     close s when s isnt closed
     ...

Related Syntax