|
|
#lang racket/base
|
|
|
(require "define.rkt")
|
|
|
(require "coerce.rkt" "len.rkt" racket/list racket/set racket/sequence racket/stream racket/dict)
|
|
|
|
|
|
(define (sliceable-container? x)
|
|
|
(ormap (λ(proc) (proc x)) (list list? string? symbol? vector? path? (λ(i) (and (not (dict? i)) (sequence? i))))))
|
|
|
|
|
|
(define (gettable-container? x)
|
|
|
(ormap (λ(proc) (proc x)) (list sliceable-container? dict?)))
|
|
|
|
|
|
|
|
|
(define/contract+provide (get container start [end #f])
|
|
|
((gettable-container? any/c) ((or/c (and/c integer? positive?) #f)) . ->* . any/c)
|
|
|
|
|
|
(define result
|
|
|
;; use handler to capture error & print localized error message
|
|
|
(with-handlers ([exn:fail? (λ(exn) (error (format "get: couldn’t retrieve ~a from ~a" (if end (format "items ~a through ~a" start end) (format "item ~a" start)) container)))])
|
|
|
(let ([end (if (and (equal? end #f) (sliceable-container? container)) (add1 start) end)])
|
|
|
(cond
|
|
|
[(list? container) (for/list ([i (in-range start end)]) (list-ref container i))]
|
|
|
[(vector? container) (for/vector ([i (in-range start end)]) (vector-ref container i))]
|
|
|
[(string? container) (substring container start end)]
|
|
|
[(symbol? container) (->symbol (get (->string container) start end))]
|
|
|
[(path? container) (get (explode-path container) start end)]
|
|
|
[(dict? container) (dict-ref container start)]
|
|
|
[(sequence? container) (get (->list container) start end)]
|
|
|
[else (error)]))))
|
|
|
|
|
|
;; don't return single-item results inside a list
|
|
|
;; check for integer because integers don't have length
|
|
|
(if (and (not (integer? result)) (= (len result) 1) (sliceable-container? container))
|
|
|
(car (->list result))
|
|
|
result))
|
|
|
|
|
|
(define (listlike-container? container)
|
|
|
(ormap (λ(pred) (pred container)) (list vector? set? sequence?)))
|
|
|
|
|
|
(define/contract+provide (in? item container)
|
|
|
(any/c any/c . -> . coerce/boolean?)
|
|
|
(cond
|
|
|
[(list? container) (member item container)]
|
|
|
[(dict? container) (dict-has-key? container item)]
|
|
|
[(path? container) (in? (->path item) (explode-path container))]
|
|
|
[(stringish? container) (regexp-match (->string item) (->string container))]
|
|
|
;; location relevant because dicts and strings are also listlike (= sequences)
|
|
|
[(listlike-container? container) (in? item (->list container))]
|
|
|
[else #f]))
|