What is scheme's equivalent of tuple unpacking?

Question

In Python, I can do something like this:

t = (1, 2) a, b = t 

...and a will be 1 and b will be 2. Suppose I have a list '(1 2) in Scheme. Is there any way to do something similar with let? If it makes a difference, I'm using Racket.

Answer 1

In racket you can use match,

(define t (list 1 2)) (match [(list a b) (+ a b)]) 

and related things like match-define:

(match-define (list a b) (list 1 2)) 

and match-let

(match-let ([(list a b) t]) (+ a b)) 

That works for lists, vectors, structs, etc etc. For multiple values, you'd use define-values:

(define (t) (values 1 2)) (define-values (a b) (t)) 

or let-values. But note that I can't define t as a "tuple" since multiple values are not first class values in (most) scheme implementations.