In Hemlock all text is in some line. Text is broken into lines wherever it contains a newline character; newline characters are never stored, but are assumed to exist between every pair of lines. The implicit newline character is treated as a single character by the text primitives.
This function returns t if line is a line object, otherwise nil.
Given a line, this function returns as a simple string the characters in
the line. This is setf’able to set the line-string to any string that
does not contain newline characters. It is an error to destructively modify
the result of line-string or to destructively modify any string after the
line-string of some line has been set to that string.
Given a line, line-previous returns the previous line or nil if there
is no previous line. Similarly, line-next returns the line following
line or nil.
This function returns the buffer which contains this line. Since a
line may not be associated with any buffer, in which case line-buffer
returns nil.
This function returns the number of characters in the line. This excludes the newline character at the end.
This function returns the character at position index within line. It
is an error for index to be greater than the length of the line or less
than zero. If index is equal to the length of the line, this returns a
#\newline character.
This function returns the property-list for line. setf, getf,
putf and remf can be used to change properties. This is typically used
in conjunction with line-signature to cache information about the line’s
contents.
This function returns an object that serves as a signature for a line’s contents. It is guaranteed that any modification of text on the line will result in the signature changing so that it is not eql to any previous value. The signature may change even when the text remains unmodified, but this does not happen often.