5.2.6.4 prevpage="..." and nextpage="..." attributes

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5.2.6.4 `prevpage="..."` and `nextpage="..."` attributes

The `prevpage` and `nextpage` attributes generate an `href` (5.2.6.2) attribute that respectively selects the previous and next pages of an `<al-for>` `ListIterator` (5.3.8.8).

The attribute value specifies the name of the iterator.

The generated `href` attribute is of the form current_url?name,iter=1 where current_url is the path component returned from the Python `urlparse.urlparse()` function (via the execution context `current_url()` method), name is either `prevpage` or `nextpage`, and iter is the specified iterator.

For example:

    >>> import albatross
    >>> class Ctx(albatross.SimpleContext):
    ...     def current_url(self):
    ...         return 'magic'
    ...
    >>> ctx = Ctx('.')
    >>> albatross.Template(ctx, '<magic>', '''
    ... <al-a nextpage="m">Next Page</al-a whitespace>
    ... ''').to_html(ctx)
    >>> ctx.flush_content()
    <a href="magic?nextpage,m=1">Next Page</a>