445 lines
16 KiB
Racket
445 lines
16 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 [eval-with (-> variable-mapping? any/c any)]
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[extract-symbols (-> any/c list?)]
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[any->string (-> any/c string?)]
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[stringify-variable-mapping (-> variable-mapping? string-variable-mapping?)]
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[string->any (-> string? any/c)]
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[read-org-sexp (-> string? (listof any/c))]
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[map-sexp (-> procedure? any/c any/c)]
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[unorg (-> string? (listof any/c))]
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[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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;; Contracts
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(contract-out [variable-mapping? contract?]
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[string-variable-mapping? contract?]
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[general-pair/c (-> contract? contract? contract?)])
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;; Syntax
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auto-hash-ref/explicit auto-hash-ref/:)
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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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;;; 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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;;; 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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;;; 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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;;; =========================
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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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;;; 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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;;; 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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;;; 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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;;; 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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;;; 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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;;; 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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;;; 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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;;; 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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;;; 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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;;; 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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;;; ==========================
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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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;;; 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
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[(unweighted-graph? gr) (list (v-func u) (v-func v))]
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[else (list (e-func (edge-weight gr u v))
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(v-func u) (v-func v))]))))
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(cond
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[(unweighted-graph? gr) (unweighted-graph/directed edges)]
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[else
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(weighted-graph/directed edges)]))
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;;; ===============
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;;; Pretty printing
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;;; ===============
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;;; Pretty print a set by listing its elements in alphabetic order.
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(define (pretty-print-set s)
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(string-join (sort (set-map s any->string) string<?)))
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;;; =========================
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;;; Additional list utilities
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;;; =========================
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;;; Collects labels for duplicate edges into a sets of labels.
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;;;
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;;; More precisely, given a list of edges and weights, produces a new
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;;; list of edges without duplicates, and a list of lists of weights
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;;; in which each element corresponds to the edge (the input is
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;;; suitable for graph constructors).
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(define (collect-by-key edges labels)
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(for/fold ([ht (make-immutable-hash)]
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#:result (values (hash-keys ht) (hash-values ht)))
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([e edges] [l labels])
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(hash-update ht e (λ (ls) (cons l ls)) empty)))
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;;; Like collect-by-key, but returns a list of sets of weights.
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(define (collect-by-key/sets edges labels)
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(let-values ([(es ls) (collect-by-key edges labels)])
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(values es (map list->set ls))))
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;;; Converts the values of a hash table from lists to sets.
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(define (ht-values/list->set ht)
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(for/hash ([(k v) (in-hash ht)])
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(values k (list->set v))))
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;;; Returns the key-value pairs of a given hash table in the order in
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;;; which the hash table orders them for hash-map and hash-for-each.
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(define (hash->list/ordered ht) (hash-map ht cons #t))
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;;; Given a list of lists, splits every single list at the given
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;;; position, and then returns two lists: one consisting of the first
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;;; halves, and the one consisting of the second halves.
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(define (multi-split-at lsts pos)
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(define (split-1 lst res)
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(define-values (l r) (split-at lst pos))
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(match res [(cons left right)
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(cons (cons l left) (cons r right))]))
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(match (foldr split-1 (cons '() '()) lsts)
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[(cons lefts rights) (values lefts rights)]))
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;;; Given a list of lists of the same length, transposes them.
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;;;
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;;; > (lists-transpose '((1 2) (a b)))
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;;; '((1 a) (2 b))
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;;;
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;;; This function is essentially in-parallel, wrapped in a couple
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;;; conversions.
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(define lists-transpose
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(compose sequence->list
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in-values-sequence
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((curry apply) in-parallel)))
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;;; =========
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;;; Functions
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;;; =========
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;;; Returns #t if the function has fixed arity (i.e. if it does not
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;;; take a variable number of arguments).
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(define (procedure-fixed-arity? func)
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(match (procedure-arity func)
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[(arity-at-least _) #f] [arity #t]))
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;;; ==========
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;;; Randomness
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;;; ==========
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;;; Generates a stream of inexact random numbers. The meaning of the
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;;; arguments is the same as for the function random:
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;;;
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;;; (in-randoms k) — a sequence of random exact integers in the range
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;;; 0 to k-1.
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;;;
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;;; (in-randoms min max) — a sequence of random exact integers the
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;;; range min to max-1.
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;;;
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;;; (in-randoms) — a sequence of random inexact numbers between
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;;; 0 and 1.
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(define in-random
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(case-lambda
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[() (for/stream ([i (in-naturals)]) (random))]
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[(k) (for/stream ([i (in-naturals)]) (random k))]
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[(min max) (for/stream ([i (in-naturals)]) (random min max))]))
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;;; ===========================
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;;; Additional stream utilities
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;;; ===========================
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;;; Returns the Cartesian product of the given streams. The result is
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;;; a stream whose elements are the elements of the Cartesian product.
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;;;
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;;; The implementation is inspired from the implementation of
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;;; cartesian-product in racket/list.
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(define (cartesian-product/stream . ss)
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;; Cartesian product of two streams, produces an improper pair.
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(define (cp-2 ss1 ss2)
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(for*/stream ([s1 (in-stream ss1)] [s2 (in-stream ss2)]) (cons s1 s2)))
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;; Fold-right over the list of streams. The value for the fold is a
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;; 1-value stream containing the empty list, which makes all the
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;; lists proper.
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(foldr cp-2 (sequence->stream (in-value (list))) ss))
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