getitem* and hasitem*

Runtime builtins for chained item access. These complement the compile-time item* macro: keylist is a runtime sequence, and failed lookups do not expand to nested item forms.

getitem*

Syntax: (getitem* ELEMENT KEYLIST) or (getitem* ELEMENT KEYLIST DEFAULT)

Walk ELEMENT through each key in KEYLIST left to right (same nesting shape as item*).

When DEFAULT is supplied, return it on LookupError at any step (including KeyError and IndexError). When DEFAULT is omitted, LookupError propagates. Other exceptions always propagate.

An empty KEYLIST raises ValueError.

(getitem* tbl #["a" "b"])
(getitem* tbl #["a" "b"] missing)
(getitem* vec #[0 1])

Keys are passed through as written, so a nested list or tuple takes integers.

hasitem*

Syntax: (hasitem* ELEMENT KEYLIST)

Walk ELEMENT through each key in KEYLIST left to right. Return true only when every step succeeds; return false on the first failed lookup without raising.

Any exception during lookup is treated as absent.

An empty KEYLIST raises ValueError.

(hasitem* tbl #["a" "b"])
(hasitem* vec #[0 1])

Comparison

Form	Kind	On missing link
*`item`**	compile-time macro	raises (via `item`)
*`getitem`**	runtime builtin	`DEFAULT` on `LookupError`, or raises without default
*`hasitem`**	runtime builtin	false
*`getattr`**	runtime builtin	chained attribute access (see getattr* and hasattr*)