Multiple Values in CL The language Common lisp is described in the ANSI standard INCITS 226-1994 (R2004) and has many implementations. Each can implement multiple values as it sees fit, and they are allowed, of course, to cons up a list for them (in fact, the Emacs Lisp compatibility layer for CL does just that … Read more
Strictly speaking, funcall would not be needed, but there are some lisps (lisp-2 variants, such as Common Lisp) that separate the variable name space of the function name space. Lisp-1 variants (e.g. Scheme) do not make this distinction. More specifically, in your case, test-func is in the variable name space. (defun foo (test-func args) (funcall … Read more
The actual meaning of F is often forgotten. According to some sources, f suffix could stand for: Field (see for example this answer) Form (as seen in various teaching materials and manuals) However, according to Gabriel and Steele’s The Evolution of Lisp, SETF comes from Peter Deutsch’s A Lisp Machine with Very Compact Programs (published … Read more
Use the built-in “+” or “-” functions, or their shorthand “1+” or “1-“, if you just want to use the result, without modifying the original number (the argument). If you do want to modify the original place (containing a number), then use the built-in “incf” or “decf” functions. Using the addition operator: (setf num 41) … Read more
setq assigns a value to a variable, whereas let introduces new variables/bindings. E.g., look what happens in (let ((x 3)) (print x) ; a (let ((x 89)) (print x) ; b (setq x 73) (print x)) ; c (print x)) ; d 3 ; a 89 ; b 73 ; c 3 ; d The … Read more
Even if possible, such redefinitions are not something that you should do without really understanding how the system will react to this. For example, if you redefine +, will any other code break? The answer to that in Racket’s case is “no” — but this is because you don’t really get to redefine +: instead, … Read more
With alists, you usually add a new cons in front of the old one to “shadow” the old value, like so: (add-to-list ‘a1 ‘(:k1 10)) After you do this (assoc :k1 a1) will return 10. If you want to “undo” your change so assoc again returns your old value, use this code: (setq a1 (delq … Read more
In Common Lisp, ‘1 is shorthand for (QUOTE 1). When evaluated, (QUOTE something) returns the something part, unevaluated. However, there is no difference between 1 evaluated and 1 unevaluated. So there is a difference to the reader: ‘1 reads as (QUOTE 1) and 1 reads as 1. But there is no difference when evaluted.
The Lisp dialect Clojure seems to be growing in popularity – you might ask out at http://clojure.org/ in one of the forums to see what real-world apps people are building with it.
See Common Lisp Implementations: A Survey by Daniel Weinreb.