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| java.lang.Object
 com.sun.java_cup.internal.runtime.virtual_parse_stack
| virtual_parse_stack | | public class virtual_parse_stack (Code) | | This class implements a temporary or "virtual" parse stack that
replaces the top portion of the actual parse stack (the part that
has been changed by some set of operations) while maintaining its
original contents. This data structure is used when the parse needs
to "parse ahead" to determine if a given error recovery attempt will
allow the parse to continue far enough to consider it successful. Once
success or failure of parse ahead is determined the system then
reverts to the original parse stack (which has not actually been
modified). Since parse ahead does not execute actions, only parse
state is maintained on the virtual stack, not full Symbol objects.
See Also: com.sun.java_cup.internal.runtime.lr_parser
version:
last updated: 7/3/96
author:
Frank Flannery |
| Field Summary | |
| protected int | real_next
Top of stack indicator for where we leave off in the real stack.
This is measured from top of stack, so 0 would indicate that no
elements have been "moved" from the real to virtual stack. | | protected Stack | real_stack
The real stack that we shadow. | | protected Stack | vstack
The virtual top portion of the stack. |
| Constructor Summary | |
| public | virtual_parse_stack(Stack shadowing_stack)
Constructor to build a virtual stack out of a real stack. |
| Method Summary | |
| public boolean | empty()
Indicate whether the stack is empty. | | protected void | get_from_real()
Transfer an element from the real to the virtual stack. | | public void | pop()
Pop the stack. | | public void | push(int state_num)
Push a state number onto the stack. | | public int | top()
Return value on the top of the stack (without popping it). |
| real_next | | protected int real_next(Code) | | Top of stack indicator for where we leave off in the real stack.
This is measured from top of stack, so 0 would indicate that no
elements have been "moved" from the real to virtual stack.
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| real_stack | | protected Stack real_stack(Code) | | The real stack that we shadow. This is accessed when we move off
the bottom of the virtual portion of the stack, but is always left
unmodified.
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| vstack | | protected Stack vstack(Code) | | The virtual top portion of the stack. This stack contains Integer
objects with state numbers. This stack shadows the top portion
of the real stack within the area that has been modified (via operations
on the virtual stack). When this portion of the stack becomes empty we
transfer elements from the underlying stack onto this stack.
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| virtual_parse_stack | | public virtual_parse_stack(Stack shadowing_stack) throws java.lang.Exception(Code) | | Constructor to build a virtual stack out of a real stack.
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| empty | | public boolean empty()(Code) | | Indicate whether the stack is empty.
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| get_from_real | | protected void get_from_real()(Code) | | Transfer an element from the real to the virtual stack. This assumes
that the virtual stack is currently empty.
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| push | | public void push(int state_num)(Code) | | Push a state number onto the stack.
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