Oracle Forms Developer – Form Builder Reference, Volume 1

*/
prefix := ’GLOBAL.’ || the_stackname;
/*
** This named stack’s pointer resides in
** GLOBAL._PTR Remember that this is the *name*
** of the pointer.
*/
ptr_name := prefix || ’_PTR’;
/*
** Force a default value of NULL so we can test if the
** pointer exists (as a global variable). If it does not
** exist, we can test in a moment for the NULL, and avoid
** the typical error due to referencing non-existent
** global variables.
*/
Default_Value( NULL, ptr_name );
/*
** If the *value* contained in the pointer is NULL, then
** the pointer must not have existed prior to the
** Default_Value statement above. Return the constant
** NO_SUCH_STACK in this case and erase the global
** variable that the Default_Value implicitly created.
*/
IF Name_In( ptr_name ) IS NULL THEN
the_val := NO_SUCH_STACK;
Erase( ptr_name );
/*
** Otherwise, the named stack already exists. Get the
** index of the largest stack element from this stack’s
** pointer.
*/
ELSE
cur_idx := Name_In( ptr_name ) ;
/*
** If the index is zero, then the named stack is already
** empty, so return the constant EMPTY_STACK, and leave
** the stack’s pointer around for later use, ie don’t
** ERASE it.
**
** Note that a stack can only be empty if some values
** have been PUSH’ed and then all values subsequently
** POP’ed. If no values were ever PUSH’ed on this named
** stack, then no associated stack pointer would have
** been created, and we would flag that error with the
** NO_SUCH_STACK case above.
*/
IF cur_idx = ’0’ THEN
the_val := EMPTY_STACK;
/*
** If the index is non-zero, then:
** (1) Determine the name of the global variable in
** which the value to be POP’ed is stored,
** GLOBAL.
** (2) Get the value of the (cur_idx)-th element to
** return
** (3) Decrement the stack pointer
** (4) Erase the global variable which was used for
** value storage
*/
ELSE
elt_name:= prefix || cur_idx;
the_val := Name_In( elt_name );
new_idx := TO_CHAR( TO_NUMBER( Name_In(ptr_name) ) - 1 ) ;
Copy( new_idx , ptr_name );
Erase( elt_name );
293