8a19f60386
- Reorder README to have implementation list after "learning tool" bullet. - This also moves tests/ and libs/ into impls. It would be preferrable to have these directories at the top level. However, this causes difficulties with the wasm implementations which need pre-open directories and have trouble with paths starting with "../../". So in lieu of that, symlink those directories to the top-level. - Move the run_argv_test.sh script into the tests directory for general hygiene.
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Notes on the mal implementation in Perl5.
This implementation should work in any perl from 5.19.3 onwards.
Earlier versions are likely to work too as long as you install a new
List::Util. The implementation uses the experimental switch
feature, which may make it vulnerable to future changes in perl.
Mal objects are all in subclasses of Mal::Type, and can be treated
as scalar, array, or hash references as appropriate.
Metadata support uses Hash::Util::FieldHash to attach external
metadata to objects. This means that in the metadata system imposes
no overhead on the normal use of objects.
Hash-maps are slightly magical. They're keyed by the stringified
versions of mal objects, and Mal::Scalar overloads stringification
so that this works properly.
Tail-call optimisation uses Perl's built-in goto &NAME syntax for
explicit tail calls. This allows functions defined by fn* to be
implemented as functions at the Perl layer.
Perl's garbage-collection is based on reference counting. This means
that reference loops will cause memory leaks, and in particular using
def! to define a function will cause that function to have a
reference to the environment it's defined in, making a small reference
loop and hence a memory leak. This can be avoided by carefully
undefining any function before it goes out of scope.