I think @Vijay’s answer is the best one so far and I just intend to Erlangify it. Pairs (cons cells) in Erlang are written as [Head|Tail] and nil is written as []. There is no restriction as to what the head and tail are but if you use the tail to chain more cons cells … Read more
With lexical scope one does not have access to variables that are not in the current scope. You also cannot pass lexical variables to other functions directly. Lisp evaluates variables and passes the values bound to these variables. There is nothing like first-class references to variables. Think functional! (let ((a 1)) (values (lambda (new-value) (setf … Read more
Lisp WAS used in AI until the end of the 1980s. In the 80s, though, Common Lisp was oversold to the business world as the “AI language”; the backlash forced most AI programmers to C++ for a few years. These days, prototypes usually are written in a younger dynamic language (Perl, Python, Ruby, etc) and … Read more
I was actually trying to do this today, and I found typing this into the CLisp REPL worked: (EXT:SAVEINITMEM “executable.exe” :QUIET t :INIT-FUNCTION ‘main :EXECUTABLE t :NORC t) where main is the name of the function you want to call when the program launches, :QUIET t suppresses the startup banner, and :EXECUTABLE t makes a … Read more
A lambda (or closure) encapsulates both the function pointer and variables. This is why, in C#, you can do: int lessThan = 100; Func<int, bool> lessThanTest = delegate(int i) { return i < lessThan; }; I used an anonymous delegate there as a closure (it’s syntax is a little clearer and closer to C than … Read more
There are several ways to introduce variables. DEFVAR and DEFPARAMETER introduce global dynamic variables. DEFVAR optionally sets it to some value, unless it is already defined. DEFPARAMETER sets it always to the provided value. SETQ does not introduce a variable. (defparameter *number-of-processes* 10) (defvar *world* (make-world)) ; the world is made only once. Notice that … Read more
It’s pretty well-known that general function equality is undecidable in general, so you’ll have to pick a subset of the problem that you’re interested in. You might consider some of these partial solutions: Presburger arithmetic is a decidable fragment of first-order logic + arithmetic. The universe package offers function equality tests for total functions with … Read more
To give the short answer, macros are used for defining language syntax extensions to Common Lisp or Domain Specific Languages (DSLs). These languages are embedded right into the existing Lisp code. Now, the DSLs can have syntax similar to Lisp (like Peter Norvig’s Prolog Interpreter for Common Lisp) or completely different (e.g. Infix Notation Math … Read more
A list in Scheme is either the empty list () (also known as nil in some Lisps), or a cons cell whose car (also known as first) is an element of the list and whose cdr (also known as rest) is either the rest of the list (i.e., another list), or an atom that terminates … Read more
The following is an implementation of tail recursion modulo cons optimization, resulting in a fully tail recursive code. It copies the input structure and then appends the new element to it, by mutation, in the top-down manner. Since this mutation is done to its internal freshly-created data, it is still functional on the outside (does … Read more