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Project's home: http://www.hexstreamsoft.com/projects/destructuring-bind-star/ UNSUPPORTED. UNSTABLE. INCOMPLETE. destructuring-bind-star is a Common Lisp library providing an enhanced (insane?) version of DESTRUCTURING-BIND. DESTRUCTURING-BIND* is 95% backwards-compatible with DESTRUCTURING-BIND (fixing a few "bugs") and additionally provides nil-as-ignore, &doc, &decl, &transform, &entire, &head, &tail, ©, &share and &setf. Here's an overview of the enhanced features, explained in detail in the comprehensive documentation: - nil-as-ignore: It's easy to unconditionally match and ignore a part of the pattern by providing NIL where a variable name is allowed. - Support for extraction of docstrings and declarations with the &doc and &decl lambda keywords. - Support for (functional) transformations, which allows one to do some "normalization" of the rest of the pattern prior to further processing, with &transform. This notably helps with the recurrent pattern of having a symbol be equivalent to a list with that symbol, as seen in LET bindings, various parts of destructuring bindings, class slots, and many other places. - &entire can be used after a transform (or many transforms) to capture what &whole at the start of that recursive pattern would have captured, except that any transforms before that &entire lambda keyword are visible. This lets you use destructuring patterns "for normalization", especially when used with nil-as-ignore. &doc and &decl can also count as a transformation (or rather, normalization) that &entire can capture: the docstring and declarations will be appear in the same order as &doc and &decl were specified, no matter how they appeared in the matched expression. - &tail is much like &rest except it can be inserted almost anywhere (and at multiple places) in the pattern, capturing the rest of the matched value. &tail doesn't affect the semantics of the pattern, for instance &tail in a pattern that accepts exactly 3 arguments still accepts exactly 3 arguments. &tail can also be used in the middle of &key parameters. In this case, the captured value is the one that &rest would have captured before &key, but with any keyword parameters before the &tail keyword removed. - &head is the "complement" of &tail, it captures a copy of all the matched pattern up to that point. - Support for flexible copying and sharing with © and &share. - Support for easy destructive modification with &setf. &setf is used with a variable in the pattern. Within the body of DESTRUCTURING-BIND*, the variable is a SETFable place that can update the original matched expression or a copy of it, depending on if &setf is in the scope of &share (the default) or ©. If there are variables "downstream" in the pattern, they are automatically updated to reflect the modification. Additionally, the following "bugs" have been fixed: - It's possible to use a variable name at the "top-level" of the pattern, matching any value. The original DESTRUCTURING-BIND has the fairly arbitrary restriction (IMHO) that it can only operate on a list. - Patterns equivalent to (&rest rest) can match any object, not just a list. This nicely mirrors the way (a &rest rest) can match a cons with any value whatsoever in the CDR. This library is in the Public Domain. See the UNLICENSE file for details.