Checking if all values of a list are true

Checking if all values of a list are true

[Nordlöw]

How do I check if all values of a list are true?

This is my attempt:
(reduce 'and '(t t))

but I get the error: and (invalid-function and)

(functionp 'and)

gives true so why on earth doesn't this work?


Thanks in advance,
Nordlöw

Re: Checking if all values of a list are true

[Nordlöw]

On 11 Juli, 13:23, Nordlöw <per.nord...@gmail.com> wrote:
> How do I check if all values of a list are true?
>
> This is my attempt:
> (reduce 'and '(t t))
>
> but I get the error: and (invalid-function and)
>
> (functionp 'and)
>
> gives true so why on earth doesn't this work?
>
> Thanks in advance,
> Nordlöw

Is there an alternative pure emacs-lisp way (non common-lisp (cl)) of
doing this?

/Nordlöw

Re: Checking if all values of a list are true

[Nordlöw]

On 11 Juli, 13:33, Nordlöw <per.nord...@gmail.com> wrote:
> On 11 Juli, 13:23, Nordlöw <per.nord...@gmail.com> wrote:
>
> > How do I check if all values of a list are true?
>
> > This is my attempt:
> > (reduce 'and '(t t))
>
> > but I get the error: and (invalid-function and)
>
> > (functionp 'and)
>
> > gives true so why on earth doesn't this work?
>
> > Thanks in advance,
> > Nordlöw
>
> Is there an alternative pure emacs-lisp way (non common-lisp (cl)) of
> doing this?
>
> /Nordlöw

It would be even better if Emacs already had a function typically
named any-p(arg-list) that returned t if all values in arg-list are
non-nil.

/Nordlöw

Re: Checking if all values of a list are true

[Florian Beck]

Nordlöw <per.nordlow@gmail.com> writes:

> On 11 Juli, 13:33, Nordlöw <per.nord...@gmail.com> wrote:
>> On 11 Juli, 13:23, Nordlöw <per.nord...@gmail.com> wrote:
>>
>> > How do I check if all values of a list are true?
>>
>> > This is my attempt:
>> > (reduce 'and '(t t))
>>
>> > but I get the error: and (invalid-function and)
>>
>> > (functionp 'and)
>>
>> > gives true so why on earth doesn't this work?

Maybe because 'and is a special form, not a function.

Try (reduce #'(lambda (x y) (and x y)) '(t t t t t t t))

> It would be even better if Emacs already had a function typically
> named any-p(arg-list) that returned t if all values in arg-list are
> non-nil.

Something like

(defmacro every-p (list)
  (cons 'and (eval list)))

CL has 'every:

(every 'eval '(t t t))
-- 
Florian Beck

Re: Checking if all values of a list are true

[Joost Kremers]

Nordlöw wrote:
> It would be even better if Emacs already had a function typically
> named any-p(arg-list) that returned t if all values in arg-list are
> non-nil.

(defmacro all-true (lst)
  `(and ,@lst)

AND is not a function (or a macro) but a special form. in my emacs (GNU
Emacs 23.0.60.1), (functionp and) returns nil, not t. which is presumably
why functions such as reduce, funcall, mapcar etc. do not accept it as an
argument.


-- 
Joost Kremers                                      joostkremers@yahoo.com
Selbst in die Unterwelt dringt durch Spalten Licht
EN:SiS(9)

Re: Checking if all values of a list are true

[David Kastrup]

Nordlöw <per.nordlow@gmail.com> writes:

> How do I check if all values of a list are true?
>
> This is my attempt:
> (reduce 'and '(t t))
>
> but I get the error: and (invalid-function and)
>
> (functionp 'and)
>
> gives true so why on earth doesn't this work?

Special form.  Try

(not (memq nil '(t t)))

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum