gdb: Iterators In Guile
23.3.3.25 Iterators In Guile
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A simple iterator facility is provided to allow, for example, iterating
over the set of program symbols without having to first construct a list
of all of them. A useful contribution would be to add support for SRFI
41 and SRFI 45.
-- Scheme Procedure: make-iterator object progress next!
A '<gdb:iterator>' object is constructed with the 'make-iterator'
procedure. It takes three arguments: the object to be iterated
over, an object to record the progress of the iteration, and a
procedure to return the next element in the iteration, or an
implementation chosen value to denote the end of iteration.
By convention, end of iteration is marked with
'(end-of-iteration)', and may be tested with the
'end-of-iteration?' predicate. The result of '(end-of-iteration)'
is chosen so that it is not otherwise used by the '(gdb)' module.
If you are using '<gdb:iterator>' in your own code it is your
responsibility to maintain this invariant.
A trivial example for illustration's sake:
(use-modules (gdb iterator))
(define my-list (list 1 2 3))
(define iter
(make-iterator my-list my-list
(lambda (iter)
(let ((l (iterator-progress iter)))
(if (eq? l '())
(end-of-iteration)
(begin
(set-iterator-progress! iter (cdr l))
(car l)))))))
Here is a slightly more realistic example, which computes a list of
all the functions in 'my-global-block'.
(use-modules (gdb iterator))
(define this-sal (find-pc-line (frame-pc (selected-frame))))
(define this-symtab (sal-symtab this-sal))
(define this-global-block (symtab-global-block this-symtab))
(define syms-iter (make-block-symbols-iterator this-global-block))
(define functions (iterator-filter symbol-function? syms-iter))
-- Scheme Procedure: iterator? object
Return '#t' if OBJECT is a '<gdb:iterator>' object. Otherwise
return '#f'.
-- Scheme Procedure: iterator-object iterator
Return the first argument that was passed to 'make-iterator'. This
is the object being iterated over.
-- Scheme Procedure: iterator-progress iterator
Return the object tracking iteration progress.
-- Scheme Procedure: set-iterator-progress! iterator new-value
Set the object tracking iteration progress.
-- Scheme Procedure: iterator-next! iterator
Invoke the procedure that was the third argument to
'make-iterator', passing it one argument, the '<gdb:iterator>'
object. The result is either the next element in the iteration, or
an end marker as implemented by the 'next!' procedure. By
convention the end marker is the result of '(end-of-iteration)'.
-- Scheme Procedure: end-of-iteration
Return the Scheme object that denotes end of iteration.
-- Scheme Procedure: end-of-iteration? object
Return '#t' if OBJECT is the end of iteration marker. Otherwise
return '#f'.
These functions are provided by the '(gdb iterator)' module to assist
in using iterators.
-- Scheme Procedure: make-list-iterator list
Return a '<gdb:iterator>' object that will iterate over LIST.
-- Scheme Procedure: iterator->list iterator
Return the elements pointed to by ITERATOR as a list.
-- Scheme Procedure: iterator-map proc iterator
Return the list of objects obtained by applying PROC to the object
pointed to by ITERATOR and to each subsequent object.
-- Scheme Procedure: iterator-for-each proc iterator
Apply PROC to each element pointed to by ITERATOR. The result is
unspecified.
-- Scheme Procedure: iterator-filter pred iterator
Return the list of elements pointed to by ITERATOR that satisfy
PRED.
-- Scheme Procedure: iterator-until pred iterator
Run ITERATOR until the result of '(pred element)' is true and
return that as the result. Otherwise return '#f'.
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