703 lines
25 KiB
Racket
703 lines
25 KiB
Racket
#lang racket
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;;; dds/utils
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;;; Various utilities.
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(require
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graph
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(for-syntax syntax/parse racket/list))
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(provide
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;; Functions
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(contract-out [unstringify-pairs (-> (listof (general-pair/c string? any/c))
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(listof (general-pair/c symbol? any/c)))]
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[read-org-variable-mapping (-> string? variable-mapping?)]
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[unorgv (-> string? variable-mapping?)]
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[dotit (-> graph? void?)]
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[read-symbol-list (-> string? (listof symbol?))]
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[drop-first-last (-> string? string?)]
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[list-sets->list-strings (-> (listof (set/c any/c)) (listof string?))]
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[pretty-print-set-sets (-> (set/c (set/c symbol?) #:kind 'dont-care) string?)]
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[update-vertices/unweighted (-> graph? (-> any/c any/c) graph?)]
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[update-graph (->* (graph?)
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(#:v-func (-> any/c any/c)
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#:e-func (-> any/c any/c))
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graph?)]
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[pretty-print-set (-> generic-set? string?)]
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[collect-by-key (-> (listof any/c) (listof any/c) (values (listof any/c) (listof (listof any/c))))]
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[collect-by-key/sets (-> (listof any/c) (listof any/c) (values (listof any/c) (listof (set/c any/c))))]
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[ht-values/list->set (-> (hash/c any/c (listof any/c)) (hash/c any/c (set/c any/c)))]
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[hash->list/ordered (-> hash? (listof (cons/c any/c any/c)))]
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[multi-split-at (-> (listof (listof any/c)) number?
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(values (listof (listof any/c)) (listof (listof any/c))))]
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[lists-transpose (-> (listof (listof any/c)) (listof (listof any/c)))]
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[procedure-fixed-arity? (-> procedure? boolean?)]
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[in-random (case-> (-> (stream/c (and/c real? inexact? (>/c 0) (</c 1))))
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(-> (integer-in 1 4294967087) (stream/c exact-nonnegative-integer?))
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(-> exact-integer? (integer-in 1 4294967087)
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(stream/c exact-nonnegative-integer?)))]
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[cartesian-product/stream (->* () #:rest (listof stream?) stream?)]
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[boolean-power (-> number? (listof (listof boolean?)))]
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[boolean-power/stream (-> number? (stream/c (listof boolean?)))]
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[any->01 (-> any/c (or/c 0 1))]
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[01->boolean (-> (or/c 0 1) boolean?)]))
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(module+ test
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(require rackunit))
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;;; ===================
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;;; HashTable Injection
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;;; ===================
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;;; This section of the file contains some utilities to streamline the
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;;; usage of hash tables mapping symbols to values. The goal is
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;;; essentially to avoid having to write explicit hash-ref calls.
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;;; A variable mapping is a hash table mapping symbols to values.
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(define (variable-mapping? dict) (hash/c symbol? any/c))
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;;; Given a (HashTable Symbol a) and a sequence of symbols, binds
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;;; these symbols to the values they are associated to in the hash
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;;; table, then puts the body in the context of these bindings.
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;;;
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;;; > (let ([ht #hash((a . 1) (b . 2))])
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;;; (auto-hash-ref/explicit (ht a b) (+ a (* 2 b))))
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;;; 5
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;;;
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;;; Note that only one expression can be supplied in the body.
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(define-syntax (auto-hash-ref/explicit stx)
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(syntax-parse stx
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[(_ (ht:id xs:id ...) body:expr)
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#`(let #,(for/list ([x (syntax->list #'(xs ...))])
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#`[#,x (hash-ref ht '#,x)])
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body)]))
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(module+ test
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(test-case "auto-hash-ref/explicit"
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(define mytable #hash((a . 3) (b . 4)))
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(check-equal? (auto-hash-ref/explicit (mytable b a)
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(* a b))
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12)
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(define ht #hash((a . #t) (b . #f)))
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(check-equal? (auto-hash-ref/explicit (ht a b)
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(and (not a) b))
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#f)))
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;;; Given an expression and a (HashTable Symbol a), looks up the
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;;; symbols with a leading semicolon and binds them to the value they
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;;; are associated to in the hash table.
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;;;
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;;; > (let ([ht #hash((a . 1) (b . 2))])
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;;; (auto-hash-ref/: ht (+ :a (* 2 :b))))
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;;; 5
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;;;
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;;; Note that the symbol :a is matched to the key 'a in the hash
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;;; table.
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;;;
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;;; Note that only one expression can be supplied in the body.
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(define-syntax (auto-hash-ref/: stx)
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(syntax-parse stx
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[(_ ht:id body)
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(let* ([names/: (collect-colons (syntax->datum #'body))])
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#`(let #,(for/list ([x names/:])
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;; put x in the same context as body
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#`[#,(datum->syntax #'body x)
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(hash-ref ht '#,(strip-colon x))])
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body))]))
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(module+ test
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(test-case "auto-hash-ref/:"
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(define ht1 #hash((x . #t) (y . #t) (t . #f)))
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(define z #t)
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(check-equal? (auto-hash-ref/: ht1
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(and :x (not :y) z (or (and :t) :x)))
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#f)
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(define ht2 #hash((a . 1) (b . 2)))
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(check-equal? (auto-hash-ref/: ht2 (+ :a (* 2 :b)))
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5)))
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;;; The helper functions for auto-hash-ref/:.
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(begin-for-syntax
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;; Collect all the symbols starting with a colon in datum.
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(define (collect-colons datum)
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(remove-duplicates
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(flatten
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(for/list ([token datum])
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(cond
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[(symbol? token)
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(let ([name (symbol->string token)])
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(if (eq? #\: (string-ref name 0))
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token
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'()))]
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[(list? token)
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(collect-colons token)]
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[else '()])))))
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;; Strip the leading colon off x.
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(define (strip-colon x)
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(let ([x-str (symbol->string x)])
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(if (eq? #\: (string-ref x-str 0))
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(string->symbol (substring x-str 1))
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x))))
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;;; Temporarily injects the mappings from the given hash table as
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;;; bindings in a namespace including racket/base and then evaluates
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;;; the expression.
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;;;
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;;; > (let ([ht #hash((a . 1) (b . 1))])
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;;; (eval-with ht '(+ b a 1)))
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;;; 3
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;;;
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;;; The local bindings from the current lexical scope are not
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;;; conserved. Therefore, the following outputs an error about a
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;;; missing identifier:
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;;;
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;;; > (let ([ht #hash((a . 1) (b . 1))]
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;;; [z 1])
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;;; (eval-with ht '(+ b z a 1)))
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;;;
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(define (eval-with ht expr)
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(parameterize ([current-namespace (make-base-namespace)])
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(for ([(x val) ht]) (namespace-set-variable-value! x val))
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(eval expr)))
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(module+ test
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(test-case "eval-with"
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(check-equal? (let ([ht #hash((a . 1) (b . 1))])
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(eval-with ht '(+ b a 1)))
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3)))
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;;; Same as eval-with, but returns only the first value produced by
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;;; the evaluated expression.
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(define (eval-with1 ht expr)
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(let ([vals (call-with-values (λ () (eval-with ht expr))
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(λ vals vals))])
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(car vals)))
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;;; ==============================
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;;; Analysis of quoted expressions
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;;; ==============================
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;;; Produces a list of symbols appearing in the quoted expression
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;;; passed in the first argument.
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(define (extract-symbols form)
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(match form
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[(? symbol?) (list form)]
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[(? list?) (flatten (for/list ([x form])
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(extract-symbols x)))]
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[else '()]))
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(module+ test
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(test-case "extract-symbols"
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(check-equal? (extract-symbols '(1 (2 3) x (y z 3)))
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'(x y z))))
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;;; =========================
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;;; Interaction with Org-mode
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;;; =========================
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;;; Org-mode supports laying out the output of code blocks as tables,
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;;; which is very practical for various variable mappings (e.g.,
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;;; states). However, when the hash table maps variables to lists,
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;;; Org-mode will create a column per list element, which may or may
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;;; not be the desired effect. In this section I define some
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;;; utilities for nicer interoperation with Org-mode tables. I also
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;;; define some shortcuts to reduce the number of words to type when
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;;; using dds with Org-mode. See example.org for examples of usage.
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;;; Converts any value to string.
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(define (any->string x)
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(with-output-to-string (λ () (display x))))
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(module+ test
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(test-case "any->string"
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(check-equal? (any->string 'a) "a")
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(check-equal? (any->string '(a 1 (x y))) "(a 1 (x y))")
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(check-equal? (any->string "hello") "hello")))
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;;; A string variable mapping is a mapping from variables to strings.
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(define (string-variable-mapping? dict) (hash/c symbol? string?))
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;;; Converts all the values of a variable mapping to string.
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(define (stringify-variable-mapping ht)
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(for/hash ([(key val) ht]) (values key (any->string val))))
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(module+ test
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(test-case "stringify-variable-mapping"
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(define mp (stringify-variable-mapping #hash((a . (and a b)) (b . (not b)))))
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(check-equal? (hash-ref mp 'a) "(and a b)")
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(check-equal? (hash-ref mp 'b) "(not b)")))
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;;; Reads any value from string.
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(define (string->any str)
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(with-input-from-string str (λ () (read))))
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(module+ test
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(test-case "string->any"
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(check-equal? (string->any "(or b (not a))") '(or b (not a)))
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(check-equal? (string->any "14") 14)))
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;;; Given a sexp, converts all "#f" to #f and "#t" to #t.
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;;;
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;;; When I read Org-mode tables, I pump them through a call to the
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;;; prin1 because the elisp sexp seems incompatible with Racket. On
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;;; the other hand, Racket Booleans seem to upset elisp a little, so
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;;; prin1 wraps them in additional double quotes. This function
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;;; removes those quotes.
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(define/match (handle-org-booleans datum)
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[("#t") #t]
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[("#f") #f]
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[((? list?)) (map handle-org-booleans datum)]
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[ (_) datum])
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;;; Given a sexp, applies the given function to any object which is
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;;; not a list.
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;;;
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;;; The contract of this function will not check whether func is
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;;; indeed applicable to every non-list element of the sexp. If this
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;;; is not the case, a contract violation for func will be generated.
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(define (map-sexp func sexp)
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(match sexp
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[(? list?) (map ((curry map-sexp) func) sexp)]
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[datum (func datum)]))
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(module+ test
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(test-case "map-sexp"
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(check-equal? (map-sexp add1 '(1 2 (4 10) 3)) '(2 3 (5 11) 4))))
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;;; Reads a sexp from a string produced by Org-mode for a named table.
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;;; See example.org for examples.
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(define read-org-sexp
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(compose ((curry map-sexp) (match-lambda
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[(and (? string?) str) (string->any str)]
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[x x]))
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string->any))
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;;; A shortcut for read-org-sexp.
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(define unorg read-org-sexp)
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(module+ test
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(test-case "read-org-sexp"
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(check-equal? (read-org-sexp "((\"a\" \"(and a b)\") (\"b\" \"(or b (not a))\"))")
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'((a (and a b)) (b (or b (not a)))))
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(check-equal? (read-org-sexp "(#t \"#t\" \"#t \" '(1 2 \"#f\"))")
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'(#t #t #t '(1 2 #f)))))
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;;; A contract allowing pairs constructed via cons or via list.
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(define (general-pair/c key-contract val-contract)
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(or/c (list/c key-contract val-contract)
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(cons/c key-contract val-contract)))
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;;; Given a list of pairs of strings and some other values (possibly
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;;; strings), converts the first element of each pair to a string, and
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;;; reads the second element with string->any or keeps it as is if it
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;;; is not a string.
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(define (unstringify-pairs pairs)
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(for/list ([p pairs])
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(match p
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[(list key val)
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(cons (string->symbol key) (if (string? val)
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(string->any val)
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val))]
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[(cons key val) ; also handle improper pairs
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(cons (string->symbol key) (if (string? val)
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(string->any val)
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val))])))
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(module+ test
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(test-case "unstringify-pairs"
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(check-equal? (unstringify-pairs '(("a" . "1") ("b" . "(and a (not b))")))
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'((a . 1) (b . (and a (not b)))))
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(check-equal? (unstringify-pairs '(("a" . 1) ("b" . "(and a (not b))")))
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'((a . 1) (b . (and a (not b)))))))
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;;; Reads a variable mapping from a string, such as the one which
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;;; Org-mode produces from tables.
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(define read-org-variable-mapping
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(compose make-immutable-hash unstringify-pairs string->any))
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(module+ test
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(test-case "read-org-variable-mapping"
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(define m1 (read-org-variable-mapping "((\"a\" \"(and a b)\") (\"b\" \"(or b (not a))\"))"))
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(define m2 (read-org-variable-mapping "((\"a\" . \"(and a b)\") (\"b\" . \"(or b (not a))\"))"))
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(define m3 (unorgv "((\"a\" . \"(and a b)\") (\"b\" . \"(or b (not a))\"))"))
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(check-equal? (hash-ref m1 'a) '(and a b))
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(check-equal? (hash-ref m2 'a) '(and a b))
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(check-equal? (hash-ref m3 'a) '(and a b))
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(check-equal? (hash-ref m1 'b) '(or b (not a)))
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(check-equal? (hash-ref m2 'b) '(or b (not a)))
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(check-equal? (hash-ref m3 'b) '(or b (not a)))))
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;;; A synonym for read-org-variable-mapping.
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(define unorgv read-org-variable-mapping)
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;;; Typeset the graph via graphviz and display it.
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(define dotit (compose display graphviz))
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;;; Reads a list of symbols from a string.
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(define (read-symbol-list str)
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(string->any (string-append "(" str ")")))
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(module+ test
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(test-case "read-symbol-list"
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(check-equal? (read-symbol-list "a b c") '(a b c))))
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;;; Removes the first and the last symbol of a given string.
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;;;
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;;; Useful for removing the parentheses in string representations of
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;;; lists.
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(define (drop-first-last str)
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(substring str 1 (- (string-length str) 1)))
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(module+ test
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(test-case "drop-first-last"
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(check-equal? (drop-first-last "(a b)") "a b")))
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;;; Converts a list of sets of symbols to a list of strings containing
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;;; those symbols.
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(define (list-sets->list-strings lst)
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(map (compose drop-first-last any->string set->list) lst))
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(module+ test
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(test-case "list-sets->list-strings"
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(check-equal? (list-sets->list-strings (list (set 'x 'y) (set 'z) (set) (set 't)))
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'("y x" "z" "" "t"))))
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;;; Pretty-prints a set of sets of symbols.
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;;;
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;;; Typically used for pretty-printing the annotations on the edges of
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;;; the state graph.
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(define (pretty-print-set-sets ms)
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(string-join (for/list ([m ms]) (format "{~a}" (pretty-print-set m))) ""))
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(module+ test
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(test-case "pretty-print-set-sets"
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(check-equal? (pretty-print-set-sets (set (set 'a 'b) (set 'c))) "{a b}{c}")))
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;;; ==========================
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;;; Additional graph utilities
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;;; ==========================
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;;; Apply a transformation to every vertex in the unweighted graph,
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;;; return the new graph. If the transformation function maps two
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;;; vertices to the same values, these vertices will be merged in the
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;;; resulting graph. The transformation function may be called
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;;; multiple times for the same vertex.
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;;;
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;;; This function does not rely on rename-vertex!, so it can be used
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;;; to permute vertex labels.
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(define (update-vertices/unweighted gr func)
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(unweighted-graph/directed
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(for/list ([e (in-edges gr)])
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(match-let ([(list u v) e])
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(list (func u) (func v))))))
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(module+ test
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(test-case "update-vertices/unweighted"
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(define gr1 (directed-graph '((a b) (b c))))
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(define gr2 (undirected-graph '((a b) (b c))))
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(define dbl (λ (x) (let ([x-str (symbol->string x)])
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(string->symbol (string-append x-str x-str)))))
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(define new-gr1 (update-vertices/unweighted gr1 dbl))
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(define new-gr2 (update-vertices/unweighted gr2 dbl))
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(check-false (has-vertex? new-gr1 'a))
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(check-true (has-vertex? new-gr1 'aa))
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(check-false (has-vertex? new-gr1 'b))
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(check-true (has-vertex? new-gr1 'bb))
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(check-false (has-vertex? new-gr1 'c))
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(check-true (has-vertex? new-gr1 'cc))
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(check-true (has-edge? new-gr1 'aa 'bb))
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(check-true (has-edge? new-gr1 'bb 'cc))
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(check-true (has-edge? new-gr2 'aa 'bb))
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(check-true (has-edge? new-gr2 'bb 'aa))
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(check-true (has-edge? new-gr2 'bb 'cc))
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(check-true (has-edge? new-gr2 'cc 'bb))))
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;;; Given a graph, apply a transformation v-func to every vertex label
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;;; and, if the graph is a weighted graph, the transformation e-func
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;;; to every edge label. Both transformations default to identity
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;;; functions. If gr is an weighted graph, the result is a weighted
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;;; graph. If gr is an unweighted graph, the result is an unweighted
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;;; graph.
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(define (update-graph gr
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#:v-func [v-func identity]
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#:e-func [e-func identity])
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(define edges
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(for/list ([e (in-edges gr)])
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(match-let ([(list u v) e])
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||
(cond
|
||
[(unweighted-graph? gr) (list (v-func u) (v-func v))]
|
||
[else (list (e-func (edge-weight gr u v))
|
||
(v-func u) (v-func v))]))))
|
||
(cond
|
||
[(unweighted-graph? gr) (unweighted-graph/directed edges)]
|
||
[else
|
||
(weighted-graph/directed edges)]))
|
||
|
||
(module+ test
|
||
(test-case "update-graph"
|
||
(define gr1 (directed-graph '((a b) (b c))))
|
||
(define gr2 (undirected-graph '((a b) (b c))))
|
||
(define dbl (λ (x) (let ([x-str (symbol->string x)])
|
||
(string->symbol (string-append x-str x-str)))))
|
||
(define new-gr1-ug (update-graph gr1 #:v-func dbl))
|
||
(define new-gr2-ug (update-graph gr2 #:v-func dbl))
|
||
(define gr3 (weighted-graph/directed '((10 a b) (11 b c))))
|
||
(define new-gr3 (update-graph gr3 #:v-func dbl #:e-func (λ (x) (* 2 x))))
|
||
|
||
(check-false (has-vertex? new-gr1-ug 'a))
|
||
(check-true (has-vertex? new-gr1-ug 'aa))
|
||
(check-false (has-vertex? new-gr1-ug 'b))
|
||
(check-true (has-vertex? new-gr1-ug 'bb))
|
||
(check-false (has-vertex? new-gr1-ug 'c))
|
||
(check-true (has-vertex? new-gr1-ug 'cc))
|
||
(check-true (has-edge? new-gr1-ug 'aa 'bb))
|
||
(check-true (has-edge? new-gr1-ug 'bb 'cc))
|
||
|
||
(check-true (has-edge? new-gr2-ug 'aa 'bb))
|
||
(check-true (has-edge? new-gr2-ug 'bb 'aa))
|
||
(check-true (has-edge? new-gr2-ug 'bb 'cc))
|
||
(check-true (has-edge? new-gr2-ug 'cc 'bb))
|
||
|
||
(check-true (has-edge? new-gr3 'aa 'bb))
|
||
(check-false (has-edge? new-gr3 'bb 'aa))
|
||
(check-true (has-edge? new-gr3 'bb 'cc))
|
||
(check-false (has-edge? new-gr3 'cc 'bb))
|
||
(check-equal? (edge-weight new-gr3 'aa 'bb) 20)
|
||
(check-equal? (edge-weight new-gr3 'bb 'cc) 22)))
|
||
|
||
|
||
;;; ===============
|
||
;;; Pretty printing
|
||
;;; ===============
|
||
|
||
;;; Pretty print a set by listing its elements in alphabetic order.
|
||
(define (pretty-print-set s)
|
||
(string-join (sort (set-map s any->string) string<?)))
|
||
|
||
(module+ test
|
||
(test-case "pretty-print-set"
|
||
(check-equal? (pretty-print-set (set 'a 'b 1)) "1 a b")))
|
||
|
||
|
||
;;; ======================================
|
||
;;; Additional list and hash map utilities
|
||
;;; ======================================
|
||
|
||
;;; Collects labels for duplicate edges into a sets of labels.
|
||
;;;
|
||
;;; More precisely, given a list of edges and weights, produces a new
|
||
;;; list of edges without duplicates, and a list of lists of weights
|
||
;;; in which each element corresponds to the edge (the input is
|
||
;;; suitable for graph constructors).
|
||
(define (collect-by-key edges labels)
|
||
(for/fold ([ht (make-immutable-hash)]
|
||
#:result (values (hash-keys ht) (hash-values ht)))
|
||
([e edges] [l labels])
|
||
(hash-update ht e (λ (ls) (cons l ls)) empty)))
|
||
|
||
(module+ test
|
||
(test-case "collect-by-key"
|
||
(define-values (e1 l1) (collect-by-key '((1 2) (1 3)) '(a b)))
|
||
(define-values (e2 l2) (collect-by-key '((1 2) (1 2)) '(a b)))
|
||
(check-equal? e1 '((1 2) (1 3))) (check-equal? l1 '((a) (b)))
|
||
(check-equal? e2 '((1 2))) (check-equal? l2 '((b a)))))
|
||
|
||
;;; Like collect-by-key, but returns a list of sets of weights.
|
||
(define (collect-by-key/sets edges labels)
|
||
(let-values ([(es ls) (collect-by-key edges labels)])
|
||
(values es (map list->set ls))))
|
||
|
||
(module+ test
|
||
(test-case "collect-by-key/sets"
|
||
(define-values (e3 l3) (collect-by-key/sets '(a b a) '(1 2 1)))
|
||
(check-equal? e3 '(a b)) (check-equal? l3 (list (set 1) (set 2)))))
|
||
|
||
;;; Converts the values of a hash table from lists to sets.
|
||
(define (ht-values/list->set ht)
|
||
(for/hash ([(k v) (in-hash ht)])
|
||
(values k (list->set v))))
|
||
|
||
(module+ test
|
||
(test-case "ht-values/list->set"
|
||
(check-equal? (ht-values/list->set #hash((a . (1 1))))
|
||
(hash 'a (set 1)))))
|
||
|
||
;;; Returns the key-value pairs of a given hash table in the order in
|
||
;;; which the hash table orders them for hash-map and hash-for-each.
|
||
(define (hash->list/ordered ht) (hash-map ht cons #t))
|
||
|
||
(module+ test
|
||
(test-case "hash->list/ordered"
|
||
(check-equal? (hash->list/ordered #hash((b . 1) (a . 1)))
|
||
'((a . 1) (b . 1)))))
|
||
|
||
;;; Given a list of lists, splits every single list at the given
|
||
;;; position, and then returns two lists: one consisting of the first
|
||
;;; halves, and the one consisting of the second halves.
|
||
(define (multi-split-at lsts pos)
|
||
(for/fold ([lefts '()]
|
||
[rights '()]
|
||
#:result (values (reverse lefts) (reverse rights)))
|
||
([lst (in-list lsts)])
|
||
(define-values (left right) (split-at lst pos))
|
||
(values (cons left lefts) (cons right rights))))
|
||
|
||
(module+ test
|
||
(test-case "multi-split-at"
|
||
(define-values (l1 l2) (multi-split-at '((1 2 3) (a b c)) 2))
|
||
(check-equal? l1 '((1 2) (a b))) (check-equal? l2 '((3) (c)))))
|
||
|
||
;;; Given a list of lists of the same length, transposes them.
|
||
;;;
|
||
;;; > (lists-transpose '((1 2) (a b)))
|
||
;;; '((1 a) (2 b))
|
||
;;;
|
||
;;; This function is essentially in-parallel, wrapped in a couple
|
||
;;; conversions.
|
||
(define lists-transpose
|
||
(compose sequence->list
|
||
in-values-sequence
|
||
((curry apply) in-parallel)))
|
||
|
||
(module+ test
|
||
(test-case "lists-transpose"
|
||
(check-equal? (lists-transpose '((1 2) (a b))) '((1 a) (2 b)))))
|
||
|
||
|
||
;;; =========
|
||
;;; Functions
|
||
;;; =========
|
||
|
||
;;; Returns #t if the function has fixed arity (i.e. if it does not
|
||
;;; take a variable number of arguments).
|
||
(define (procedure-fixed-arity? func)
|
||
(match (procedure-arity func)
|
||
[(arity-at-least _) #f] [arity #t]))
|
||
|
||
(module+ test
|
||
(test-case "procedure-fixed-arity?"
|
||
(check-true (procedure-fixed-arity? not))
|
||
(check-false (procedure-fixed-arity? +))))
|
||
|
||
|
||
;;; ==========
|
||
;;; Randomness
|
||
;;; ==========
|
||
|
||
;;; Generates a stream of inexact random numbers. The meaning of the
|
||
;;; arguments is the same as for the function random:
|
||
;;;
|
||
;;; (in-randoms k) — a sequence of random exact integers in the range
|
||
;;; 0 to k-1.
|
||
;;;
|
||
;;; (in-randoms min max) — a sequence of random exact integers the
|
||
;;; range min to max-1.
|
||
;;;
|
||
;;; (in-randoms) — a sequence of random inexact numbers between
|
||
;;; 0 and 1.
|
||
(define in-random
|
||
(case-lambda
|
||
[() (for/stream ([i (in-naturals)]) (random))]
|
||
[(k) (for/stream ([i (in-naturals)]) (random k))]
|
||
[(min max) (for/stream ([i (in-naturals)]) (random min max))]))
|
||
|
||
(module+ test
|
||
(test-case "in-random"
|
||
(random-seed 0)
|
||
(check-equal? (stream->list (stream-take (in-random 100) 10))
|
||
'(85 65 20 40 89 45 54 38 26 62))
|
||
(check-equal? (stream->list (stream-take (in-random 50 100) 10))
|
||
'(75 59 82 85 61 85 59 64 75 53))
|
||
(check-equal? (stream->list (stream-take (in-random) 10))
|
||
'(0.1656109603231493
|
||
0.9680391127132195
|
||
0.051518813640790355
|
||
0.755901955353936
|
||
0.5923534604277275
|
||
0.5513340634474264
|
||
0.7022057040731392
|
||
0.48375400938578744
|
||
0.7538961707172924
|
||
0.01828428516237329))))
|
||
|
||
|
||
;;; ===========================
|
||
;;; Additional stream utilities
|
||
;;; ===========================
|
||
|
||
|
||
;;; Returns the Cartesian product of the given streams. The result is
|
||
;;; a stream whose elements are the elements of the Cartesian product.
|
||
;;;
|
||
;;; The implementation is inspired from the implementation of
|
||
;;; cartesian-product in racket/list.
|
||
(define (cartesian-product/stream . ss)
|
||
;; Cartesian product of two streams, produces an improper pair.
|
||
(define (cp-2 ss1 ss2)
|
||
(for*/stream ([s1 (in-stream ss1)] [s2 (in-stream ss2)]) (cons s1 s2)))
|
||
;; Fold-right over the list of streams. The value for the fold is a
|
||
;; 1-value stream containing the empty list, which makes all the
|
||
;; lists proper.
|
||
(foldr cp-2 (sequence->stream (in-value (list))) ss))
|
||
|
||
(module+ test
|
||
(test-case "cartesian-product/stream"
|
||
(check-equal? (stream->list (cartesian-product/stream (in-range 3) (in-range 4 6) '(a b)))
|
||
'((0 4 a)
|
||
(0 4 b)
|
||
(0 5 a)
|
||
(0 5 b)
|
||
(1 4 a)
|
||
(1 4 b)
|
||
(1 5 a)
|
||
(1 5 b)
|
||
(2 4 a)
|
||
(2 4 b)
|
||
(2 5 a)
|
||
(2 5 b)))))
|
||
|
||
|
||
;;; ==================
|
||
;;; Boolean operations
|
||
;;; ==================
|
||
|
||
;;; Returns the n-th Cartesian power of the Boolean domain: {0,1}^n.
|
||
(define (boolean-power n) (apply cartesian-product (make-list n '(#f #t))))
|
||
|
||
(module+ test
|
||
(test-case "boolean-power"
|
||
(check-equal? (boolean-power 2) '((#f #f) (#f #t) (#t #f) (#t #t)))))
|
||
|
||
;;; Like boolean-power, but returns a stream whose elements the
|
||
;;; elements of the Cartesian power.
|
||
(define (boolean-power/stream n) (apply cartesian-product/stream (make-list n '(#f #t))))
|
||
|
||
(module+ test
|
||
(test-case "boolean-power/stream"
|
||
(check-equal? (stream->list (boolean-power/stream 2)) '((#f #f) (#f #t) (#t #f) (#t #t)))))
|
||
|
||
;;; Converts any non-#f value to 1 and #f to 0.
|
||
(define (any->01 x) (if x 1 0))
|
||
|
||
(module+ test
|
||
(test-case "any->01"
|
||
(check-equal? (any->01 #t) 1)
|
||
(check-equal? (any->01 #f) 0)))
|
||
|
||
;;; Converts 0 to #f and 1 to #t
|
||
(define (01->boolean x)
|
||
(case x [(0) #f] [else #t]))
|
||
|
||
(module+ test
|
||
(test-case "01->boolean"
|
||
(check-equal? (01->boolean 0) #f)
|
||
(check-equal? (01->boolean 1) #t)))
|