The generic function
stream-start-line-p
returns
t
if
stream
is positioned at the beginning of a line, and
nil
otherwise. It is permissible to define a method that always returns
nil
.
Note that although a value of 0 from
stream-line-column
also indicates the beginning of a line, there are cases where
stream-start-line-p
can be meaningfully implemented and
stream-line-column
cannot. For example, for a window using variable-width characters the column number is not very meaningful, whereas the beginning of a line has a clear meaning.
The default method for
stream-start-line-p
on class
fundamental-character-output-stream
uses
stream-line-column
. Therefore, if this is defined to return
nil
, a method should be provided for either
stream-start-line-p
or
stream-fresh-line
.