Task

Given a prompt and a list containing a number of strings of which one is to be selected, create a function that:

 prints a textual menu formatted as an index value followed by its corresponding string for each item in the list;
 prompts the user to enter a number;
 returns the string corresponding to the selected index number.


The function should reject input that is not an integer or is out of range by redisplaying the whole menu before asking again for a number. The function should return an empty string if called with an empty list.

For test purposes use the following four phrases in a list:

   fee fie
   huff and puff
   mirror mirror
   tick tock

Note

This task is fashioned after the action of the Bash select statement.

FUNCTION bashMenu RETURNS CHAR(
   i_c AS CHAR
):
 
   DEF VAR ii        AS INT.
   DEF VAR hfr       AS HANDLE.
   DEF VAR hmenu     AS HANDLE EXTENT.
   DEF VAR ikey      AS INT.
   DEF VAR ireturn   AS INT INITIAL ?.
 
   EXTENT( hmenu ) = NUM-ENTRIES( i_c ).
 
   CREATE FRAME hfr ASSIGN
      WIDTH    =  80
      HEIGHT   =  NUM-ENTRIES( i_c )
      PARENT   =  CURRENT-WINDOW
      VISIBLE  =  TRUE
      .
 
   DO ii = 1 TO NUM-ENTRIES( i_c ):
 
      CREATE TEXT hmenu ASSIGN
         FRAME          =  hfr
         FORMAT         =  "x(79)"
         SCREEN-VALUE   =  SUBSTITUTE( "&1. &2", ii, ENTRY( ii, i_c ) )
         ROW            =  ii
         VISIBLE        =  TRUE
         .
 
   END.
 
   IF i_c = "" THEN
      ireturn = 1.
 
   DO WHILE ireturn = ?:
 
      READKEY.
      ikey = INTEGER( CHR( LASTKEY ) ) NO-ERROR.
      IF ikey >= 1 AND ikey <= NUM-ENTRIES( i_c ) THEN
         ireturn = ikey.
 
   END. 
 
   RETURN ENTRY( ireturn, i_c ).
 
END FUNCTION.
 
MESSAGE 
   bashMenu( "fee fie,huff and puff,mirror mirror,tick tock" )
VIEW-AS ALERT-BOX.