gistfile1.rkt

#lang racket

(require data/heap)

(struct item
        (timestamp priority id event)
        #:transparent)

; x < yなら#t, x > yなら#fを返す。
; x = yなら、bodyの評価結果を返す。
(define-syntax-rule
  (<>-or x y body)

  (let ([rx x]
        [ry y])
    (if (< rx ry)
      #t
      (if (> rx ry)
        #f
        body))))

(define (event<=? e1 e2)
  (<>-or (item-timestamp e1) (item-timestamp e2)
         (<>-or (item-priority e1) (item-priority e2)
                (<>-or (item-id e1) (item-id e2)
                       #t))))

(define heap (make-heap event<=?))

(heap-add! heap (item 0 0 1 -1))
(heap-add! heap (item 0 0 0 -2))

(displayln (heap-min heap))

(displayln "こんにちは、世界")

(flush-output)