find-symbol

(find-symbol string [package])

Like intern but never creates: returns the symbol package -- the current package by default -- makes accessible under the name, nil otherwise. Accessible means a symbol present in the package (what intern, export, import, shadowing-import and shadow recorded in its member table, or a definition made under it -- a defun is an interning), a symbol inherited from a package it uses (that package's exports), a standard name reached through cl, or a keyword. A symbol merely read in the source under the package is not recorded, and a name unintern took out is no longer the package's own. A designator that names no package (nil included) signals a package-error whose package-error-package is the designator, as in Common Lisp — a probe for an optional system guards on find-package first.

Deviations from Common Lisp: on the compiled backends (JVM/WASM) only a literal string can answer nil for a read/compile-time package — the check is folded at compile time against the compile-time view (cl symbols plus the program's own defuns), so runtime-defined variables and macros are not visible there (the interpreter checks the live image, including global variables and defmacro macros). A computed name is interned instead, so it always yields a symbol, and its status is read off the spelling that lowering builds (:external for a qualified one, :internal for a bare one) rather than from the image. What the package itself records or reaches from another package answers as on the interpreter, literal or computed: a symbol it imports (:import-from, a re-export), a symbol it inherits through :use (the used package's symbol, :inherited), and a member its defpackage records (:shadow, :intern). So does a standard name a package reaches through cl -- the cl symbol, :inherited -- under a computed name or package as under a literal one: a program with such a lookup carries a table of the standard names. Two corners keep the built answer: a computed designator naming a pre-seeded shim package (uiop, bordeaux-threads, closer-common-lisp) builds PKG:NAME, and the one-argument form's status for a computed standard name stays :internal unless a multiple-value form reads it in place or the program carries the table anyway. A package the program creates with make-package is the exception: its member table is consulted on every backend, so nil before an intern and the symbol after hold there whatever the arguments. The function object #'find-symbol answers the same two values; on the compiled backends its arguments are computed ones.

With common-lisp (or cl) as the package, the answer is the standard's name list: CLHS 11.1.2.1 makes the package export all 978 standard names, so a name is found whether or not rontolisp implements an operator behind one. Being exported is not being defined — fboundp, macro-function and special-operator-p still answer nil for such a name, calling it still signals undefined-function, and a program may still defun it. A package that uses cl inherits those names the same way (:inherited), and t and nil come back as themselves.

A second value reports the ANSI accessibility status of the name in that package — :external, :inherited, :internal, or nil when the package does not provide it, so the two values are nil together: