In Scheme you'd define it like this:
- (letrec [(get_length (lambda (lst) (if (null? lst) 0 [+ 1 (get_length (cdr lst))] )) )]
+ (letrec [(get_length
+ (lambda (lst) (if (null? lst) 0 [+ 1 (get_length (cdr lst))] )) )]
... ; here you go on to use the function "get_length"
)