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Solving LeetCode problems with Racket: I don't know what I expected

• gus_massa 2y ago
  > You might think “So what’s the big deal? It’s not statically typed, just runtime-enforced contracts.” and you’re completely right. That said, the trick is going to come in handy soon. If you use typed/racket, they compiler checks a lot of them at compilation time, and even use them to eliminate implicit types checks. > (let ([huge-list (range 1e7)]) > (begin > (displayln (current-process-milliseconds)) > (first (map add1 huge-list)) > (displayln (current-process-milliseconds)) > ) > ) There is some magic when you use in-range inside map like: > (first (map add1 (in-range 1e7))) It would be nice if the compiler can automatically fix this examplet, but it has to be an incredible smart compiler. > Let’s take a look at how the Racket standard library implements this macro (this is what proper Racket formatting looks like, apparently). A lot of Racket is written in a simplified version of Racket informally call #'kernel. The problem is that #'kernel is very difficult to use because it has only the minimal stuff. One of the first definitions is `and`, so that explains the ugly definition. After a few modules that add more and more friendly tools, it's possible to define `and` as (define-syntax (my-and stx) (syntax-case stx () [(_) #'#t] [(_ x) #'x] [(_ x y ...) #'(if x (my-and y ...) #f)]))