Tips for golfing in Racket / Scheme

In Racket, λ and lambda are synonymous keywords for constructing anonymous functions, but λ is 2 bytes where lambda is 6.

In Scheme, there's no such keyword λ and you're stuck with lambda.

Use ~a to convert numbers and symbols to strings.

When using Racket, bind variables using λ to shave off a few bytes. In Scheme, lambda makes this trick not applicable, unless one is binding four or more variables.

Example: One variable saves 2 bytes over let/define

(define n 55)(* n n) ; 20 bytes

(let([n 55])(* n n)) ; 20 bytes

((λ(n)(* n n))55) ; 18 bytes