newbie question regarding sharp-quote

[Rajesh Kommu]

The following works as expected:

(funcall #'+ 1 2 3) ; => 6

but

(funcall '+ 1 2 3)

works too! Don't I always need a sharp-quote to get a function object?

thanks in advance,

rk

[Ken Tilton]

Rajesh Kommu wrote:
> The following works as expected:
>
> (funcall #'+ 1 2 3) ; => 6
>
> but
>
> (funcall '+ 1 2 3)
>
> works too! Don't I always need a sharp-quote to get a function object?

No, /funcall/ needs a function designator, of which a symbol is one.
Start at funcall in the CLHS, follow the link to function designator.

kenzo

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[Giovanni Gigante]

According to the Hyperspec,
> *funcall* applies /function/ to /args/. If /function/ is a symbol, it
is coerced to a function as if by finding its functional value in the
global environment.

So (funcall '+ 1 2 3) is coerced to (funcall #'+ 1 2 3).

[George Neuner]

You need the #' (or equivalent) in situations where the symbol would
normally be evaluated as data. funcall is an exception because it
evaluates its first argument as a function.

George
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[Kent M Pitman]

Rajesh Kommu <rko...@student.physics.ucdavis.edu> writes:

> The following works as expected:
>
> (funcall #'+ 1 2 3) ; => 6
>
> but
>
> (funcall '+ 1 2 3)
>
> works too! Don't I always need a sharp-quote to get a function object?

Funcall of '+ means (funcall (symbol-function '+) ...), which does not
access the lexical environment, only the global environment;
while using #'+ means (funcall (function +) ...), where the function
special form which accesses the lexical environment.
Since you are prohibited from lexically binding +, it is unlikely you will
see a difference, since you will always be in an environment that has no
lexical bindings for + as a function. But if you were to use
'foo vs #'foo it would affect things.

(defun foo (x) x)
(flet ((foo (x) (1+ x)))
(list (funcall 'foo 1) (funcall #'foo 1)))
=> (1 2)