Comment by shakna

Probably worth noting that there's already an SRFI for this. [0] And that macro will work on any Scheme implementing the standard since about '98.

    (define-syntax rec
      (syntax-rules ()
        ((rec (NAME . VARIABLES) . BODY)
         (letrec ( (NAME (lambda VARIABLES . BODY)) ) NAME))
        ((rec NAME EXPRESSION)
         (letrec ( (NAME EXPRESSION) ) NAME))))

[0] https://srfi.schemers.org/srfi-31/srfi-31.html