17 The STREAM package

stream-start-line-p

Generic Function

Summary

A generic function that returnst if the stream is positioned at the beginning of a line.

Package

stream

Signature

stream-start-line-p stream => result

Arguments

stream: A stream.

Values

result: A boolean.

Description

The generic functionstream-start-line-p returnst if stream is positioned at the beginning of a line, andnil otherwise. It is permissible to define a method that always returnsnil.

Note that although a value of 0 fromstream-line-column also indicates the beginning of a line, there are cases wherestream-start-line-p can be meaningfully implemented andstream-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 forstream-line-start-p on classfundamental-character-output-stream usesstream-line-column. Therefore, if this is defined to returnnil, a method should be provided for eitherstream-start-line-p orstream-fresh-line.