HELP POPPROMPT Jonathan Laventhol, August 1984
The user-assignable variable POPPROMPT contains the prompt string which is
output when reading from a terminal (usually through the standard input
channel *POPDEVIN). The default value of POPPROMPT is : .
The prompt must be either a string or a procedure. If it is a string, it is
just printed when needed. If it is a procedure, then every time a prompt is
needed, the procedure is run and its result (which must be a string) is
printed. This can be used for 'intelligent' prompting; try this:
define popprompt();
popclosebracket >< ' '
enddefine;
Note: Make sure that your procedure returns exactly one result, a string. If
there are too many results they will be left on the stack, producing confusing
behaviour. If there is no result, or it's not a string, then you'll get a
mishap, which will reset the prompt to : .
See also
HELP *CHARIN - used when reading in from the terminal
REF *SYSIO - for more details on Input/Output procedures
HELP *READLINE - which also uses a prompt
--- C.all/help/popprompt
--- Copyright University of Sussex 1991. All rights reserved. ----------