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count=/ c
count>/ c
is-true/ c
arity-includes/ c
Version: 4.1.5.4

2 Contract

 (require (planet dvanhorn/ralist:1:12/contract))

Just like (planet dvanhorn/ralist:1:12/main), but with contracts.

(count=/c n)  flat-contract?
  n : natural-number/c

Returns a flat contract that requires the input to have a count equal to n.

(count>/c n)  flat-contract?
  n : natural-number/c

Returns a flat contract that requires the input to have a count greater than n.

(is-true/c x)  flat-contract?
  x : any/c

Returns a flat contract that requires nothing of its input, and returns x, i.e. it produces a contract for the predicate (lambda (_) x).

(arity-includes/c n)  flat-contract?
  n : natural-number/c

Returns a flat contract that requires its input to be a procedure accepting at least n arguments, i.e. it produces a contract for the predicate,

  (lambda (x)
    (and (procedure? x)
         (procedure-arity-includes? x n)))