All I get are "stalls" many seconds (minute) into running the game if I run it
from drracket. The command line version doesn't stutter at all. So no, running
a GC right ahead of big-bang isn't going to solve that problem.
Jack, I have taken the liberty to rewrite your game in a more Rackety style:
proceed from important functions down to unimportant ones. I have also
eliminated <* and friends. With prefix, you get (< 1 2 3 4 5 6 7 8 9)
naturally. And I have re-organized the with-chance function so that you can
tell from the header that it takes at least one argument (needed for the zero?
case).
-- Matthias
#lang racket
(require 2htdp/image 2htdp/universe)
; World constants
(define WIDTH 600)
(define HEIGHT 400)
(define BKG-IMG (rectangle WIDTH HEIGHT "solid" "black"))
;; run star wars game
(define (main)
(define player0 (list PLAYER-START-X PLAYER-START-Y (keyhash "left" "right"
"up" "down")))
(define world0 (hash 'stars '() 'player player0 'bullets '()))
(big-bang world0
(to-draw (λ (w) (player-draw w (bullets-draw w (stars-draw w
BKG-IMG)))))
(on-tick (λ (w) (player-tick (stars-tick (bullets-tick w)))))
(on-key (λ (w a-key) (player-key w a-key)))
(on-release (λ (w a-key) (bullets-release (player-release w a-key)
a-key)))))
; Player world functions
(define (player-draw w bkg)
(place-image PLAYER-IMG (first (hash-ref w 'player)) (second (hash-ref w
'player)) bkg))
(define (player-tick w)
(hash-update w 'player (λ (p) (append (key-move (take p 2) PLAYER-SPEED
(third p)) (drop p 2)))))
(define (player-key w a-key)
(hash-update w 'player (λ (p) (list (first p) (second p) (update-key (third
p) a-key)))))
(define (player-release w a-key)
(hash-update w 'player (λ (p) (list (first p) (second p) (update-release
(third p) a-key)))))
(define (player-x w)
(first (hash-ref w 'player)))
(define (player-y w)
(second (hash-ref w 'player)))
; Point utilities (Point: (List Real Real))
(define (move dx dy v) (list (+ (first v) dx) (+ (second v) dy)))
(define (move* dx dy v) (map (curry move dx dy) v))
(define (draw-at v img bkg) (place-image img (first v) (second v) bkg))
(define (bounded x1 x2 y1 y2 v) (and (< x1 (first v) x2) (< y1 (second v) y2)))
(define (filter-bounds x1 x2 y1 y2 vs) (filter (curry bounded x1 x2 y1 y2) vs))
; Player auxilary constants and functions
(define PLAYER-START-X 100)
(define PLAYER-START-Y (/ HEIGHT 2))
(define PLAYER-SPEED 2)
(define PLAYER-IMG (square 16 "solid" "red"))
; Star world functions
(define (stars-tick w)
(define h (random HEIGHT))
(filter-inworld 'stars (move-stars STAR-SPD 0 (with-chance STAR-RATE add-star
w WIDTH h))))
(define (star-draw v bkg)
(draw-at v STAR-IMG bkg))
(define (stars-draw w bkg)
(foldl star-draw bkg (hash-ref w 'stars)))
(define BULLET-IMG (square 4 "solid" "gray"))
(define BULLET-SPD 10)
(define (bullets-move w)
(hash-update w 'bullets (curry move* BULLET-SPD 0)))
(define (bullets-release w a-key)
(if (not (key=? a-key "z"))
w
(hash-update w 'bullets (λ (v) (list* (list (player-x w) (player-y w))
v)))))
(define (bullet-draw v bkg)
(place-image BULLET-IMG (first v) (second v) bkg))
(define (bullets-draw w bkg)
(foldl bullet-draw bkg (hash-ref w 'bullets)))
(define (bullets-tick w)
(filter-inworld 'bullets (bullets-move w)))
; Star auxilary constants and funtions
(define STAR-IMG (square 3 "solid" "white"))
(define STAR-SPD -8)
(define STAR-RATE 5)
(define (add-star w x y)
(hash-update w 'stars (curry cons (list x y))))
(define (move-stars dx dy w)
(hash-update w 'stars (curry map (curry move dx dy))))
(define (filter-stars w)
(hash-update w 'stars (curry filter-bounds 0 WIDTH 0 HEIGHT)))
; World utilities
(define (filter-inworld key w)
(hash-update w key (curry filter-bounds 0 WIDTH 0 HEIGHT)))
; Keyboard utilities
(define (keyhash . args)
(make-immutable-hash (map (λ (key) (cons key #f)) args)))
(define (key-move point speed keys)
(move (+ (if (hash-ref keys "left") (- speed) 0) (if (hash-ref keys "right")
speed 0))
(+ (if (hash-ref keys "up") (- speed) 0) (if (hash-ref keys "down")
speed 0))
point))
(define (update-key keys a-key) (hash-set keys a-key #t))
(define (update-release keys a-key) (hash-set keys a-key #f))
; General utilities
(define (with-chance n proc w . args)
(if (zero? (random n)) (apply proc w args) w))
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