| Remember: the specific feature of a typical Lisp is that it is written as s-expressions. S-expressions are a notation for data (similar to XML, JSON, ...). This notation is independently useful for all kinds of purposes - like a list of city names: (paris berlin london). But the specific feature of Lisp is this: code is data and data can be code. Some use the word homocionic -> the program is written in its own data syntax. S-expressions are the data syntax used by Lisp and the programs are written as s-expressions. > (+ 2 3) means apply the + function with the 2 3 arguments Depending on the context (a b c) can have different meanings.
As a list it is a list of three items. As a top-level item it is a function call. In (let (a b c) ...) it means a list of variables. Lisp is based on s-expressions. S-expressions is a simple syntax for data: an symbolic expression is: a symbol: foo, bar, 1, 2 paris, +, -, delta, bear, G1345
an empty list: NIL or ()
a non-empty list: ( s-expressionn1 ... s-expression-n)
That's basically it.Lisp has three functions to work with those: READ, PRINT and EVAL. READ reads a textual s-expression to data, PRINT takes data and prints it as an s-expression, EVAL takes data and evaluates it. Thus the toplevel of Lisp is something like (loop (print (eval (read))))
It reads a Lisp expression in form of an s-expression, evaluates it and prints the result.> AFAIK if you want a list either you use (list a b c) or you use '(a b c) which I find less regular than +(1 2) or (1 2) which is equal to list(1 2) (a b c) is a list. It's an s-expression. It is valid data. It's only valid Lisp, if A is an operator. (quote (a b c)) is also a nested list AND a valid Lisp program. But READ reads all kinds of nested lists, not just Lisp programs. It does that, because S-expressions are a general data syntax. Compare that with most other programming languages. Their programs are not written on top of a general data-structure notation like nested lists, nested vectors, nested tables, ... |