operator
true
if the stream
is attached to a destination and false
otherwise.
Replacing is
with isnt
will reverse the result.
stream-name (is | isnt) attached or #current-output (is | isnt) attached or #current-input (is | isnt) attached
is attached
is a a stream
test used to determine whether a stream
is attached to a
destination.
A stream
can have three states:
unattached
, the initial state,
When a stream
is attached, its destination can be any one of five types:
buffer
,
file
,
referent
,
string sink function
, or
#markup-parser
.
The is attached
test can also be applied to #current-input
, to determine when #current-input
can supply data to a string sink
or markup sink
.