The Best Programming Language

As Andrew Hunt and David Thomas say in the Pragmatic Programmer, there’s no such thing as the best programming language, just the best programming language for the job in hand.

However, if I had to choose the best language it would be Lisp. Here’s why:

The following code is written in Emacs Lisp. It prints out all the elements of a list

(cl-loop for element in mylist do (print element))

In the code below I’ve set mylist to equal the numbers one to five. Evaluating the loop will, unsurprisingly, print the numbers one to five.

(setq mylist '(1 2 3 4 5))
(cl-loop for element in mylist do (print element))
=> 1 
2
3
4 
5

You’re probably thinking you can do the same in Python or Java or whatever your preferred language is, and you’d be right.

But can your preferred language do this?

(setq mylist '(cl-loop for element in mylist do (print element)))
mylist
=>   (cl-loop for element in mylist do (print element))

In the above code I’ve set mylist to be the loop itself.
That means I can set the loop code to loop across itself and print itself out one word at a time.

 (cl-loop for element in mylist do (print element))
=> cl-oop 
for 
element
in
... etc 

In Lisp, code is data. So mylist is data; it’s a list of symbols: cl-loop for element etc. But I can also evaluate mylist in which case mylist will be a set of instructions to loop across itself and print itself out.

(eval mylist) 
=> cl-oop 
for 
element
in
... etc   

Or to put it another way, I’ve just written a list that can read itself!

The thing that makes this possible is the fact that Lisp is a homoiconic language: programs written in such a language can be manipulated as data using the language.

Things like this give me a warm glow inside. They remind me why I love coding so much.