NAME

Iterator - Parrot Iterator Class

DESCRIPTION

Iterators are used in combination with other classes (mainly aggregates) to visit all entries in that aggregate.

SYNOPSIS

Iterate from the beginning of the aggregate:

  .include "iterator.pasm"
    new P0, .Iterator, P1       # setup iterator for aggregate P1
    set P0, .ITERATE_FROM_START # reset iterator, begin at start
  iter_loop:
    unless P0, iter_end         # while (entries) ...
      shift P2, P0              # get entry
      ...
      branch iter_loop

The two lines of iterator creation can be short written as:

    iter P0, P1                 # create new iterator P0 for aggregate P1

This creates a new iterator and resets it.

Iterate from the end of the aggregate (Array like classes only):

  .include "iterator.pasm"
    new P0, .Iterator, P1       # setup iterator for aggregate P1
    set P0, .ITERATE_FROM_END   # reset iterator, begin at end
  iter_loop:
    unless P0, iter_end         # while (entries) ...
      pop P2, P0                # get entry
      ...
      branch iter_loop

Iterating over hashes

  .include "datatypes.pasm"     # type constants
  .include "iterator.pasm"
    new P0, .Iterator, P1       # setup iterator for hash P1
    set P0, .ITERATE_FROM_START # reset iterator, begin at start
  iter_loop:
    unless P0, iter_end         # while (entries) ...
      shift S2, P0              # get key for next entry
      typeof I0, P0[S2]         # get type of entry at key S2
      ne I0, .DATATYPE_INTVAL, no_int
      set I1, P0[S2]            # extract integer
    no_int:

      ...
      branch iter_loop

FILES

src/pmc/iterator.pmc, t/pmc/iter.t

AUTHOR

Leopold Toetsch <lt@toetsch.at>