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bug#7086: `booleanp' return value is multi-valued list
From: |
MON KEY |
Subject: |
bug#7086: `booleanp' return value is multi-valued list |
Date: |
Wed, 22 Sep 2010 17:58:12 -0400 |
"Return non-`nil' if OBJECT is one of the two canonical boolean
values: `t' or `nil'."
It should be documented both in the manual and the docstring of `booleanp' that
its return value is a list.
Specifically that the following two forms return muti-valued lists:
(booleanp t)
;=> (t)
(booleanp nil)
;=> (nil t)
Additionaly, given the nature of this function and the puposes it
might serve, it
should be documented _why_ the return value is a list.
Frustratingly, while the manual waxes on about the readers interpretation of
fundamental identity equivalence w/re `nil' and `()' and their self evaluating
specialness it has frightening little to offer w/re how one should reflect on
these things values within lisp programs.
(info "(elisp)nil and t")
In lieu of this, the terseness of the `booleanp's docstring extends a
tautological
flavor which can only be met with confusion by the uninitiated.
Indeed, while I can appreciate why (booleanp nil) returns a two element list
I'm unable to reason a rationale for why (booleanp t) doesn't?
Also, there is this goofiness:
(defun tt--bool-w/opt (&optional x)
(booleanp x))
(tt--bool-w/opt nil) ;=> (nil t)
(tt--bool-w/opt t) ;=> (t)
(tt--bool-w/opt) ;=> (nil t)
(defun tt--bool (x)
(booleanp x))
(tt--bool nil) ;=> (nil t)
(tt--bool t) ;=> (t)
(tt--bool 'nil) ;=> (nil t)
(booleanp '()) ;=> (nil t)
(booleanp ()) ;=> (nil t)
(tt--bool)
;=> Debugger entered--Lisp error:
; (wrong-number-of-arguments (lambda (x) (booleanp x)) 0)
Also, I find this above error troublesome given that the following
form returns:
(tt--bool-w/opt)
Whereas this one doesn't:
(defun tt--bool-nil (nil)
(booleanp nil))
(tt--bool-nil)
;=> Debugger entered--Lisp error:
; (wrong-number-of-arguments (lambda (nil) (booleanp nil)) 0)
(tt--bool-nil 'nil)
;=> Debugger entered--Lisp error: (setting-constant nil)
And, the nature of the above errors doesn't really stand up given that:
(defun tt--bool-qt-nil (())
(booleanp '()))
(tt--bool-qt-nil)
;=> Debugger entered--Lisp error: (wrong-number-of-arguments (lambda
(nil) (booleanp (quote nil))) 0)
(tt--bool-qt-nil nil)
;=> Debugger entered--Lisp error: (setting-constant nil)
(tt--bool-qt-nil ())
;=> Debugger entered--Lisp error: (setting-constant nil)
These last two being the most maddening.
Emacs lets me define the function but then accuses me of somthing I didn't even
(appear) to do, i.e. set the constant nil.
--
/s_P\
- bug#7086: `booleanp' return value is multi-valued list,
MON KEY <=