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181 lines
6.5 KiB
Racket
181 lines
6.5 KiB
Racket
#lang racket/base
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(require racket/contract)
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(require (only-in racket/list empty? range))
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(require (only-in racket/format ~a))
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(require (only-in racket/string string-join))
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(require (only-in racket/vector vector-member))
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(module+ test (require rackunit))
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(require "debug.rkt")
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(provide (all-defined-out))
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;; general way of coercing to string
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(define/contract (->string x)
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(any/c . -> . string?)
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(cond
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[(string? x) x]
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[(empty? x) ""]
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[(symbol? x) (symbol->string x)]
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[(number? x) (number->string x)]
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[(path? x) (path->string x)]
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[(char? x) (~a x)]
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[else (error (format "Can't make ~a into string" x))]))
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(module+ test
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(check-equal? (->string "foo") "foo")
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(check-equal? (->string '()) "")
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(check-equal? (->string 'foo) "foo")
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(check-equal? (->string 123) "123")
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(define file-name-as-text "foo.txt")
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(check-equal? (->string (string->path file-name-as-text)) file-name-as-text)
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(check-equal? (->string #\¶) "¶"))
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;; general way of coercing to symbol
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(define (->symbol thing)
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; todo: on bad input, it will pop a string error rather than symbol error
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(string->symbol (->string thing)))
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;; general way of coercing to a list
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(define (->list x)
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(any/c . -> . list?)
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(cond
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[(list? x) x]
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[(vector? x) (vector->list x)]
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[else (list x)]))
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(module+ test
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(check-equal? (->list '(1 2 3)) '(1 2 3))
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(check-equal? (->list (list->vector '(1 2 3))) '(1 2 3))
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(check-equal? (->list "foo") (list "foo")))
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;; general way of coercing to boolean
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(define (->boolean x)
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(any/c . -> . boolean?)
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;; in Racket, everything but #f is true
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(if x #t #f))
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(module+ test
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(check-true (->boolean #t))
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(check-false (->boolean #f))
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(check-true (->boolean "#f"))
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(check-true (->boolean "foo"))
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(check-true (->boolean '()))
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(check-true (->boolean '(1 2 3))))
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;; general way of asking for length
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(define (len x)
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(any/c . -> . integer?)
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(cond
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[(list? x) (length x)]
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[(string? x) (string-length x)]
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[(symbol? x) (len (->string x))]
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[(vector? x) (vector-length x)]
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[(hash? x) (len (hash-keys x))]
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[else #f]))
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(module+ test
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(check-equal? (len '(1 2 3)) 3)
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(check-not-equal? (len '(1 2)) 3) ; len 2
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(check-equal? (len "foo") 3)
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(check-not-equal? (len "fo") 3) ; len 2
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(check-equal? (len 'foo) 3)
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(check-not-equal? (len 'fo) 3) ; len 2
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(check-equal? (len (list->vector '(1 2 3))) 3)
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(check-not-equal? (len (list->vector '(1 2))) 3) ; len 2
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(check-equal? (len (make-hash '((a . 1) (b . 2) (c . 3)))) 3)
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(check-not-equal? (len (make-hash '((a . 1) (b . 2)))) 3)) ; len 2
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;; general way of fetching an item from a container
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(define/contract (get container start [end #f])
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((any/c any/c) ((λ(i)(or (integer? i) (and (symbol? i) (equal? i 'end)))))
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. ->* . any/c)
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(define (sliceable-container? container)
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(ormap (λ(proc) (proc container)) (list list? string? vector?)))
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(set! end
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(if (sliceable-container? container)
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(cond
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;; treat negative lengths as offset from end (Python style)
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[(and (integer? end) (< end 0)) (+ (len container) end)]
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;; 'end slices to the end
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[(equal? end 'end) (len container)]
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;; default to slice length of 1 (i.e, single-item retrieval)
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[(equal? end #f) (add1 start)]
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[else end])
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end))
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(define result (cond
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;; for sliceable containers, make a slice
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[(list? container) (for/list ([i (range start end)])
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(list-ref container i))]
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[(vector? container) (for/vector ([i (range start end)])
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(vector-ref container i))]
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[(string? container) (substring container start end)]
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[(symbol? container) (->symbol (get (->string container) start end))]
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;; for hash, just get item
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[(hash? container) (let ([hash-key start])
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(hash-ref container hash-key))]
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[else #f]))
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;; don't return single-item results inside a list
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(if (and (sliceable-container? result) (= (len result) 1))
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(car (->list result))
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result))
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(module+ test
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(check-equal? (get '(0 1 2 3 4 5) 2) 2)
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(check-equal? (get '(0 1 2 3 4 5) 0 2) '(0 1))
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(check-equal? (get '(0 1 2 3 4 5) 2 -1) '(2 3 4))
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(check-equal? (get '(0 1 2 3 4 5) 2 'end) '(2 3 4 5))
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(check-equal? (get (list->vector '(0 1 2 3 4 5)) 2) 2)
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(check-equal? (get (list->vector'(0 1 2 3 4 5)) 0 2) (list->vector '(0 1)))
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(check-equal? (get (list->vector'(0 1 2 3 4 5)) 2 -1) (list->vector '(2 3 4)))
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(check-equal? (get (list->vector'(0 1 2 3 4 5)) 2 'end) (list->vector '(2 3 4 5)))
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(check-equal? (get "purple" 2) "r")
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(check-equal? (get "purple" 0 2) "pu")
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(check-equal? (get "purple" 2 -1) "rpl")
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(check-equal? (get "purple" 2 'end) "rple")
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(check-equal? (get 'purple 2) 'r)
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(check-equal? (get 'purple 0 2) 'pu)
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(check-equal? (get 'purple 2 -1) 'rpl)
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(check-equal? (get 'purple 2 'end) 'rple)
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(check-equal? (get (make-hash '((a . 1) (b . 2) (c . 3))) 'a) 1))
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;; general way of testing for membership (à la Python 'in')
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(define/contract (in container item)
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(any/c any/c . -> . any/c)
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(cond
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[(list? container) (member item container)] ; returns #f or sublist beginning with item
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[(vector? container) (vector-member item container)] ; returns #f or zero-based item index
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[(hash? container)
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(and (hash-has-key? container item) (get container item))] ; returns #f or hash value
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[(string? container) (let ([result (in (map ->string (string->list container)) (->string item))])
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(if result
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(string-join result "")
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#f))] ; returns #f or substring beginning with item
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[(symbol? container) (let ([result (in (->string container) (->string item))])
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(if result
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(->symbol result)
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result))] ; returns #f or subsymbol (?!) beginning with item
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[else #f]))
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(module+ test
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(check-equal? (in '(1 2 3) 2) '(2 3))
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(check-false (in '(1 2 3) 4))
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(check-equal? (in (list->vector '(1 2 3)) 2) 1)
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(check-false (in (list->vector '(1 2 3)) 4))
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(check-equal? (in (make-hash '((a . 1) (b . 2) (c . 3))) 'a) 1)
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(check-false (in (make-hash '((a . 1) (b . 2) (c . 3))) 'x))
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(check-equal? (in "foobar" "o") "oobar")
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(check-false (in "foobar" "z"))
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(check-equal? (in 'foobar 'o) 'oobar)
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(check-false (in 'foobar 'z))
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(check-false (in #\F "F"))) |