Allison Randal wrote:
I had a much longer reply, but I'm going to let it steep overnight and
see what percolates.
I ran through a number of possibilities, but so far my favorite is:
find_global and store_global are truly 'global', that is, they always
require a fully specified namespace, including the HLL namespace.
$P0 = find_global 'bar' # the top-level namespace
$P1 = find_global 'parrot', 'bar' # 'bar' in ['parrot']
$P2 = find_global ['parrot';'Foo'], 'bar' # 'bar' in ['parrot';'Foo']
$P3 = find_global 'tcl', 'bar' # 'bar' in ['tcl']
Then a set of opcodes using the add_*, del_*, get_* naming scheme handle
the "magically assume the HLL root/current namespace" behavior. (PDD 21
uses both get_* and find_* for retrieval. It's better to standardize on
one, but it doesn't really matter which one.)
.HLL "Perl5", "perl5_group"
$P0 = get_symbol 'bar' # 'bar' in ['perl5']
$P1 = get_symbol 'Foo', 'bar' # 'bar in ['perl5';'Foo']
.namespace [ 'Foo' ]
$P2 = get_symbol 'bar' # 'bar' in ['perl5';'Foo']
(I thought about prefixing all the opcodes that assume the HLL namespace
with hll_, but since those are the common case, I'd rather mark the
rarer global case.)
The .namespace directive has more flexibility, since it's a directive
not an opcode. We can keep the basic syntax as the magical HLL behavior:
.namespace [ 'Foo' ] # namespace is ['parrot';'Foo']
.HLL "Perl5", "perl5_group" # namespace is ['perl5']
.namespace [ 'Foo' ] # namespace is ['perl5';'Foo']
If you only use .HLL and no .namespace, then it assumes the root HLL
namespace.
And add a couple of special forms for the rarer cases when you want to
set the current namespace to the HLL or global root:
.namespace hll_root
.namespace global_root
------
Here are some of the "also-ran"s, in abbreviated form:
--
We could take the Perl 5 strategy of reserving a name ('main' or 'root'
or something similar) to always act as an alias to the top-level of the
current HLL namespace.
Conclusion: Perl 5 on Parrot will use this strategy, and so might other
languages, but we shouldn't force it on all languages.
--
We could break out the root prefix from the rest of the name:
$P2 = find_global 'parrot', ['Foo'], 'bar' # bar in ['parrot';'Foo']
Conclusion: reaching the global root would require an empty prefix key
and an empty namespace name key. Not really an improvement, more of an
unprovement.
--
We could have separate opcodes for "direct access" and "hll indirect
access".
Conclusion: this led to a combinatorial explosion (bad), but then to the
simplified solution above.
--
We could assume the current HLL namespace, and call methods on the
namespace object to retrieve "meta" information like the root HLL
namespace or global namespace.
Conclusion: more complex than is necessary to solve the problem.
------
Allison
