2.28.5.4 The default compare procedure

It is convenient to have a compare procedure readily available for comparing most built in types.

Function: default-compare obj1 obj2

Compare its arguments by type using the ordering:

null < pair < boolean < char <
     < string < symbol < number < vector < other

Two objects of the same type type are compared as type-compare would, if there is such a procedure. The type null consists of the empty list (). The effect of comparing two other objects or of comparing cyclic structures (made from lists or vectors) is unspecified. (Implementations are encouraged to add comparisons for other built in types, e.g. records, regexps, etc.)

RATIONALE default-compare refines pair-compare by splitting neither-null-nor-pair.

NOTE default-compare could be defined as follows (mind the order of the cases!):

(define (default-compare x y)
  (select-compare x y
    (null?    0)
    (pair?    (default-compare (car x) (car y))
              (default-compare (cdr x) (cdr y)))
    (boolean? (boolean-compare x y))
    (char?    (char-compare    x y))
    (string?  (string-compare  x y))
    (symbol?  (symbol-compare  x y))
    (number?  (number-compare  x y))
    (vector?  (vector-compare default-compare x y))
    (else (error "unrecognized types" x y))))