f251478dd6
Entities now move smoothly between tiles instead of snapping. Previous positions are tracked in pacman and ghost ADTs; the draw layer linearly interpolates between prev and current based on movement timer progress. Residual time is carried across movement ticks for consistent speed at varying frame rates. Teleportation and ghost house exits call sync-prev! to prevent cross-map interpolation artifacts. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
115 lines
4.7 KiB
Racket
115 lines
4.7 KiB
Racket
#lang r7rs
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Ghost ADT ;;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; A ghost has a position, direction, movement mode, and type identity.
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;; The targeting AI is handled by the level — this ADT only stores state.
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;; Each ghost instance represents one of the four ghosts (Blinky, Inky,
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;; Pinky, Clyde). Contains NO graphics code.
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(define-library (pacman-project adt ghost)
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(import (scheme base)
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(pacman-project adt position))
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(export make-ghost)
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(begin
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;; make-ghost :: symbol, number, number, number, number, number -> ghost
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;; Creates a ghost of the given type at start-row/col with a scatter
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;; corner target and a house exit delay (0 = starts outside).
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(define (make-ghost ghost-type start-row start-col
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scatter-row scatter-col exit-delay)
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(let ((position (make-position start-row start-col))
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(direction 'left)
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(mode (if (= exit-delay 0) 'scatter 'in-house))
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(scatter-target (make-position scatter-row scatter-col))
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(house-timer exit-delay)
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(movement-timer 0)
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(reverse-queued? #f)
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(prev-row start-row)
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(prev-col start-col))
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;; direction! :: symbol -> /
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(define (direction! new-dir)
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(set! direction new-dir))
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;; mode! :: symbol -> /
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;; Sets the ghost mode. When switching between chase/scatter,
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;; the ghost must reverse direction (queued for next move).
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(define (mode! new-mode)
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(when (and (not (eq? mode new-mode))
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(not (eq? mode 'in-house))
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(not (eq? new-mode 'in-house)))
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(set! reverse-queued? #t))
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(set! mode new-mode))
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;; move! :: number, number -> /
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;; Saves previous position, then moves by delta.
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(define (move! delta-row delta-col)
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(set! prev-row (position 'row))
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(set! prev-col (position 'col))
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((position 'row!) (+ (position 'row) delta-row))
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((position 'col!) (+ (position 'col) delta-col)))
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;; sync-prev! :: -> /
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;; Sets previous position to current. Call after teleportation
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;; or ghost house exit to prevent long-range interpolation.
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(define (sync-prev!)
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(set! prev-row (position 'row))
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(set! prev-col (position 'col)))
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;; consume-reverse! :: -> boolean
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;; Returns #t and clears the flag if a reverse was queued.
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(define (consume-reverse!)
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(if reverse-queued?
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(begin (set! reverse-queued? #f) #t)
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#f))
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;; update-house-timer! :: number -> /
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;; Decreases house timer. When it reaches 0, ghost exits.
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(define (update-house-timer! delta-time)
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(when (eq? mode 'in-house)
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(set! house-timer (- house-timer delta-time))
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(when (<= house-timer 0)
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(set! mode 'scatter))))
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;; reset-movement-timer! :: -> /
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(define (reset-movement-timer!)
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(set! movement-timer 0))
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;; set-movement-timer! :: number -> /
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(define (set-movement-timer! val)
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(set! movement-timer val))
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;; advance-movement-timer! :: number -> number
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;; Returns updated movement timer value.
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(define (advance-movement-timer! delta-time)
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(set! movement-timer (+ movement-timer delta-time))
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movement-timer)
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;; dispatch-ghost :: symbol -> any
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(define (dispatch-ghost msg)
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(cond ((eq? msg 'position) position)
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((eq? msg 'direction) direction)
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((eq? msg 'direction!) direction!)
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((eq? msg 'type) ghost-type)
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((eq? msg 'mode) mode)
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((eq? msg 'mode!) mode!)
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((eq? msg 'move!) move!)
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((eq? msg 'prev-row) prev-row)
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((eq? msg 'prev-col) prev-col)
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((eq? msg 'sync-prev!) sync-prev!)
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((eq? msg 'scatter-target) scatter-target)
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((eq? msg 'in-house?) (eq? mode 'in-house))
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((eq? msg 'consume-reverse!) consume-reverse!)
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((eq? msg 'update-house-timer!) update-house-timer!)
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((eq? msg 'movement-timer) movement-timer)
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((eq? msg 'advance-movement-timer!) advance-movement-timer!)
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((eq? msg 'reset-movement-timer!) reset-movement-timer!)
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((eq? msg 'set-movement-timer!) set-movement-timer!)
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(else (error "Ghost ADT -- Unknown message:" msg))))
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dispatch-ghost))))
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