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pollen/readability.rkt

299 lines
11 KiB
Racket

#lang racket/base
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(require racket/contract)
(require (only-in racket/list empty? range splitf-at dropf dropf-right))
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(require (only-in racket/format ~a))
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(require (only-in racket/string string-join))
(require (only-in racket/vector vector-member))
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(require (only-in racket/set set set->list set?))
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(module+ test (require rackunit))
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(require "debug.rkt")
(provide (all-defined-out))
;; general way of coercing to integer
(define/contract (->int x)
(any/c . -> . integer?)
(cond
[(integer? x) x]
[(real? x) (floor x)]
[(and (string? x) (> (len x) 0)) (->int (string->number x))]
[(symbol? x) (->int (->string x))]
[(char? x) (char->integer x)]
[(has-length? x) (len x)]
[else (error "Can't convert to integer:" x)]))
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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?)
(cond
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[(string? x) x]
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[(empty? x) ""]
[(symbol? x) (symbol->string x)]
[(number? x) (number->string x)]
[(path? x) (path->string x)]
[(char? x) (~a x)]
[else (error (format "Can't make ~a into string" x))]))
(module+ test
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(check-equal? (->string "foo") "foo")
(check-equal? (->string '()) "")
(check-equal? (->string 'foo) "foo")
(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)
(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 path
(define (->path thing)
; todo: on bad input, it will pop a string error rather than path error
(string->path (->string thing)))
(define (->complete-path thing)
(path->complete-path (->path thing)))
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;; general way of coercing to a list
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(define/contract (->list x)
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(any/c . -> . list?)
(cond
[(list? x) x]
[(vector? x) (vector->list x)]
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[(set? x) (set->list x)]
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[else (list x)]))
(module+ test
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(check-equal? (->list '(1 2 3)) '(1 2 3))
(check-equal? (->list (list->vector '(1 2 3))) '(1 2 3))
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(check-equal? (->list (set 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 vector
(define (->vector x)
(any/c . -> . vector?)
; todo: on bad input, it will pop a list error rather than vector error
(cond
[(vector? x) x]
[else (list->vector (->list x))]))
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;; general way of coercing to boolean
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(define/contract (->boolean x)
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(any/c . -> . boolean?)
;; in Racket, everything but #f is true
(if x #t #f))
(module+ test
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(check-true (->boolean #t))
(check-false (->boolean #f))
(check-true (->boolean "#f"))
(check-true (->boolean "foo"))
(check-true (->boolean '()))
(check-true (->boolean '(1 2 3))))
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(define/contract (has-length? x)
(any/c . -> . boolean?)
(ormap (λ(proc) (proc x)) (list list? string? symbol? vector? hash? set?)))
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;; general way of asking for length
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(define/contract (len x)
(has-length? . -> . integer?)
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(cond
[(list? x) (length x)]
[(string? x) (string-length x)]
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[(symbol? x) (len (->string x))]
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[(vector? x) (len (->list x))]
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[(hash? x) (len (hash-keys x))]
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[(set? x) (len (->list x))]
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[else #f]))
(module+ test
(check-equal? (len '(1 2 3)) 3)
(check-not-equal? (len '(1 2)) 3) ; len 2
(check-equal? (len "foo") 3)
(check-not-equal? (len "fo") 3) ; len 2
(check-equal? (len 'foo) 3)
(check-not-equal? (len 'fo) 3) ; len 2
(check-equal? (len (list->vector '(1 2 3))) 3)
(check-not-equal? (len (list->vector '(1 2))) 3) ; len 2
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(check-equal? (len (set 1 2 3)) 3)
(check-not-equal? (len (set 1 2)) 3) ; len 2
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(check-equal? (len (make-hash '((a . 1) (b . 2) (c . 3)))) 3)
(check-not-equal? (len (make-hash '((a . 1) (b . 2)))) 3)) ; len 2
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(define/contract (sliceable-container? x)
(any/c . -> . boolean?)
(ormap (λ(proc) (proc x)) (list list? string? symbol? vector?)))
(define/contract (gettable-container? x)
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(any/c . -> . boolean?)
(ormap (λ(proc) (proc x)) (list sliceable-container? hash?)))
;; general way of setting an item in a mutable container
(define/contract (change x i value)
((or/c vector? hash?) any/c any/c . -> . void?)
; general-purpose mutable data object setter
(cond
[(vector? x) (vector-set! x i value)]
[(hash? x) (hash-set! x i value)]
[else (error "Can't set this datatype using change")]))
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;; general way of fetching an item from a container
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(define/contract (get container start [end #f])
((gettable-container? any/c) ((λ(i)(or (integer? i) (and (symbol? i) (equal? i 'end)))))
. ->* . any/c)
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(set! end
(if (sliceable-container? container)
(cond
;; treat negative lengths as offset from end (Python style)
[(and (integer? end) (< end 0)) (+ (len container) end)]
;; 'end slices to the end
[(equal? end 'end) (len container)]
;; default to slice length of 1 (i.e, single-item retrieval)
[(equal? end #f) (add1 start)]
[else end])
end))
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(define result (cond
;; 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)]
[(symbol? container) (->symbol (get (->string container) start end))]
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;; for hash, just get item
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[(hash? container) (hash-ref container start)]
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[else #f]))
;; don't return single-item results inside a list
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(if (and (sliceable-container? container) (= (len result) 1))
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(car (->list result))
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result))
(module+ test
(check-equal? (get '(0 1 2 3 4 5) 2) 2)
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(check-equal? (get `(0 1 ,(list 2) 3 4 5) 2) (list 2))
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(check-equal? (get '(0 1 2 3 4 5) 0 2) '(0 1))
(check-equal? (get '(0 1 2 3 4 5) 2 -1) '(2 3 4))
(check-equal? (get '(0 1 2 3 4 5) 2 'end) '(2 3 4 5))
(check-equal? (get (list->vector '(0 1 2 3 4 5)) 2) 2)
(check-equal? (get (list->vector'(0 1 2 3 4 5)) 0 2) (list->vector '(0 1)))
(check-equal? (get (list->vector'(0 1 2 3 4 5)) 2 -1) (list->vector '(2 3 4)))
(check-equal? (get (list->vector'(0 1 2 3 4 5)) 2 'end) (list->vector '(2 3 4 5)))
(check-equal? (get "purple" 2) "r")
(check-equal? (get "purple" 0 2) "pu")
(check-equal? (get "purple" 2 -1) "rpl")
(check-equal? (get "purple" 2 'end) "rple")
(check-equal? (get 'purple 2) 'r)
(check-equal? (get 'purple 0 2) 'pu)
(check-equal? (get 'purple 2 -1) 'rpl)
(check-equal? (get 'purple 2 'end) 'rple)
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(check-equal? (get (make-hash `((a . ,(list 1)) (b . ,(list 2)) (c . ,(list 3)))) 'a) (list 1)))
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;; general way of testing for membership (à la Python 'in')
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;; put item as first arg so function can use infix notation
;; (item . in . container)
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(define/contract (in? item container)
(any/c any/c . -> . boolean?)
(->boolean (cond
[(list? container) (member item container)] ; returns #f or sublist beginning with item
[(vector? container) (vector-member item container)] ; returns #f or zero-based item index
[(hash? container)
(and (hash-has-key? container item) (get container item))] ; returns #f or hash value
[(string? container) ((->string item) . in? . (map ->string (string->list container)))] ; returns #f or substring beginning with item
[(symbol? container) ((->string item) . in? . (->string container))] ; returns #f or subsymbol (?!) beginning with item
[else #f])))
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(module+ test
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(check-true (2 . in? . '(1 2 3)))
(check-false (4 . in? . '(1 2 3)))
(check-true (2 . in? . (list->vector '(1 2 3))))
(check-false (4 . in? . (list->vector '(1 2 3))))
(check-true ('a . in? . (make-hash '((a . 1) (b . 2) (c . 3)))))
(check-false ('x . in? . (make-hash '((a . 1) (b . 2) (c . 3)))))
(check-true ("o" . in? . "foobar"))
(check-false ("z" . in? . "foobar"))
(check-true ('o . in? . 'foobar))
(check-false ('z . in? . 'foobar))
(check-false ("F" . in? . #\F)))
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;; stringish: data type that can be trivially converted to string
;; todo: merge this with pathish
(define/contract (stringish? x)
(any/c . -> . boolean?)
(->boolean (or path? string? symbol?)))
;; python-style string testers
(define/contract (starts-with? str starter)
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(stringish? stringish? . -> . boolean?)
(let ([str (->string str)]
[starter (->string starter)])
(and (<= (len starter) (len str)) (equal? (get str 0 (len starter)) starter))))
(module+ test
(check-true ("foobar" . starts-with? . "foo"))
(check-true ("foobar" . starts-with? . "f"))
(check-true ("foobar" . starts-with? . "foobar"))
(check-false ("foobar" . starts-with? . "bar")))
(define/contract (ends-with? str ender)
(string? string? . -> . boolean?)
(and (<= (len ender) (len str)) (equal? (get str (- (len str) (len ender)) 'end) ender)))
(module+ test
(check-true ("foobar" . ends-with? . "bar"))
(check-true ("foobar" . ends-with? . "r"))
(check-true ("foobar" . ends-with? . "foobar"))
(check-false ("foobar" . ends-with? . "foo")))
;; trim from beginning & end of list
(define (trim items test-proc)
(list? procedure? . -> . list?)
(dropf-right (dropf items test-proc) test-proc))
(module+ test
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; (check-equal? (trim (list "\n" " " 1 2 3 "\n") whitespace?) '(1 2 3))
(check-equal? (trim (list 1 3 2 4 5 6 8 9 13) odd?) '(2 4 5 6 8)))
;; split list into list of sublists using test-proc
(define/contract (splitf-at* xs split-test)
;; todo: better error message when split-test is not a predicate
(list? predicate/c . -> . (listof list?))
(define (&splitf-at* xs [acc '()]) ; use acc for tail recursion
(if (empty? xs)
;; reverse because accumulation is happening backward
;; (because I'm using cons to push latest match onto front of list)
(reverse acc)
(let-values ([(item rest)
;; drop matching elements from front
;; then split on nonmatching
;; = nonmatching item + other elements (which will start with matching)
(splitf-at (dropf xs split-test) (compose1 not split-test))])
;; recurse, and store new item in accumulator
(&splitf-at* rest (cons item acc)))))
;; trim off elements matching split-test
(&splitf-at* (trim xs split-test)))
(module+ test
; (check-equal? (splitf-at* '("foo" " " "bar" "\n" "\n" "ino") whitespace?) '(("foo")("bar")("ino")))
(check-equal? (splitf-at* '(1 2 3 4 5 6) even?) '((1)(3)(5))))