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Function FUNCTION-LAMBDA-EXPRESSION

Syntax

  • function-lambda-expression functionlambda-expression, closure-p, name

Arguments and Values

Description

Returns information about function as follows:

The primary value, lambda-expression, is function's defining lambda expression, or nil if the information is not available. The lambda expression may have been pre-processed in some ways, but it should remain a suitable argument to compile or function. Any implementation may legitimately return nil as the lambda-expression of any function.

The secondary value, closure-p, is nil if function's definition was enclosed in the null lexical environment or something non-nil if function's definition might have been enclosed in some non-null lexical environment. Any implementation may legitimately return true as the closure-p of any function.

The tertiary value, name, is the "name" of function. The name is intended for debugging only and is not necessarily one that would be valid for use as a name in defun or function, for example. By convention, nil is used to mean that function has no name. Any implementation may legitimately return nil as the name of any function.

Examples

The following examples illustrate some possible return values, but are not intended to be exhaustive:

(function-lambda-expression #'(lambda (x) x))

NIL, false, NIL or NIL, true, NIL or (LAMBDA (X) X), true, NIL or (LAMBDA (X) X), false, NIL

(function-lambda-expression (funcall #'(lambda () #'(lambda (x) x))))

NIL, false, NIL or NIL, true, NIL or (LAMBDA (X) X), true, NIL or (LAMBDA (X) X), false, NIL

(function-lambda-expression (funcall #'(lambda (x) #'(lambda () x)) nil))

NIL, true, NIL or (LAMBDA () X), true, NIL or NIL, false, NIL or (LAMBDA () X), false, NIL

(flet ((foo (x) x)) (setf (symbol-function 'bar) #'foo) (function-lambda-expression #'bar))

NIL, false, NIL or NIL, true, NIL or (LAMBDA (X) (BLOCK FOO X)), true, NIL or (LAMBDA (X) (BLOCK FOO X)), false, FOO or (SI::BLOCK-LAMBDA FOO (X) X), false, FOO

(defun foo () (flet ((bar (x) x)) #'bar))

FOO

(function-lambda-expression (foo))

NIL, false, NIL or NIL, true, NIL or (LAMBDA (X) (BLOCK BAR X)), true, NIL or (LAMBDA (X) (BLOCK BAR X)), true, (:INTERNAL FOO 0 BAR) or (LAMBDA (X) (BLOCK BAR X)), false, "BAR in FOO"

Side Effects

None.

Affected By

None.

Exceptional Situations

None.

See Also

None.

Notes

Although implementations are free to return nil, true, nil in all cases, they are encouraged to return a lambda expression as the primary value in the case where the argument was created by a call to compile or eval (as opposed to being created by loading a compiled file).

\issue{FUNCTION-DEFINITION:JAN89-X3J13}