LabLISP Guide

FUNCTION

Function form expects one argument, most typically a symbol. It will look up a function object associated with the symbol. The FUNCTION form is related to quoting and has the special character #' (sharp-quote). A symbol in LabLISP can name a variable and a function at the same time - like in Common LISP, there are separate namespaces for values and functions. A symbol in an expression is evaluated to the function if it stands first in the form, otherwise it is evaluated to the value as variable. With sharp-quoting a symbol, we force evalation to the function named by it.

Following example should make this more clear

>(setq f 3)      ; we defined variable F, with value 3
3
 
>(defun f () 42)  ; we defined function F, with no parameters, returning 42
F

Now we have symbol F which has both value and function, let's see how it evaluates

>f                ; we are evaluating just symbol outside of form
3
 
>(+ 1 f)          ; F will be evaluated to value 3
4
 
>(f)              ; function call to F
42
 
>'f               ; quoting F
F
 
>#'f              ; (FUNCTION F) call returns the function object itself
#<user-defined function F>

See also functions SYMBOL-VALUE, SYMBOL-FUNCTION in the Package and symbol operations section, and the applicative functions FUNCALL and APPLY in Management section.

See also the future section 1.3.4 for more details.