When producing formatted output in Lisp, where should you put the newlines (e.g., before or after the line, FRESH-LINE vs TERPRI, ~& vs ~% in FORMAT)?
Where possible, it is desirable to write functions that produce output as building blocks. In contrast with other languages, which either conservatively force a newline at various times or require the program to keep track of whether it needs to force a newline, the Lisp I/O system keeps track of whether the most recently printed character was a newline or not. The function FRESH-LINE outputs a newline only if the stream is not already at the beginning of a line. TERPRI forces a newline irrespective of the current state of the stream. These correspond to the ~& and ~% FORMAT directives, respectively. (If the Lisp I/O system can’t determine whether it’s physically at the beginning of a line, it assumes that a newline is needed, just in case.) Thus, if you want formatted output to be on a line of its own, start it with ~& and end it with ~%. (Some people will use a ~& also at the end, but this isn’t necessary, since we know a priori that we’re not at the beginning of a line. The only exc
Related Questions
- When producing formatted output in Lisp, where should you put the newlines (e.g., before or after the line, FRESH-LINE vs TERPRI, ~& vs ~% in FORMAT)?
- Is it true that a component connection will only produce a 1080i output vs HDMI producing 1080p?
- How can I interface the output of the HT9200 device to the telephone line?
