Subroutine:   CANCEL

Purpose:      Remove user input from table maintained by HERMES.

Category:     USER-INTERFACE 

File:         srvreq.c

Author:       J.P. Terlouw

Use:          CALL CANCEL( KEY )        Input      character

              KEY      An ASCII string containing the keyword
                       (including = sign) of which the associated
                       values will be removed.

Examples:     Here the servant task checks on the validity of the
              input and repeats the call to obtain the input if it
              was invalid.

              .
              WHILE (.TRUE.)                      infinite loop
                 NEL = USRREAL( VALUE,..., 'V=', 'TYPE V' )
                 IF (VALUE is valid)
                 THEN
                    XWHILE            leave loop
                 ELSE
                    CALL CANCEL( 'V=' )
                 CIF
              CWHILE
              .

              In the next example the servant task performs an
              infinite loop and asks the user whether it should go
              through this loop another time.

              LOGICAL AGAIN
              .
              WHILE .TRUE.                  infinite loop
                 .
                 .
                 NEL = USERLOG( AGAIN, ..., 'AGAIN=', ...)
                 IF (AGAIN)
                 THEN
                    CALL CANCEL( 'AGAIN=' )
                 ELSE
                    XWHILE
                 CIF
              CWHILE
              .
              .

Updates:      Mar  9, 1979: original document
              Feb 15, 1990: JPT, Portable version, rewritten in ANSI C.