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Add table->function/list.

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This commit is contained in:
Sergiu Ivanov 2022-04-13 00:50:53 +02:00
parent 1503434306
commit 3b51a4ba51
2 changed files with 40 additions and 17 deletions
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36
functions.rkt
View file

@ -18,7 +18,8 @@
(provide
pseudovariadic-lambda pvλ pseudovariadic-define pvdefine
tabulate* tabulate*/strict tabulate*/pv tabulate tabulate/strict tabulate/pv
tabulate*/pv/boolean tabulate/pv/boolean tabulate*/pv/01 tabulate/pv/01)
tabulate*/pv/boolean tabulate/pv/boolean tabulate*/pv/01 tabulate/pv/01
table->function/list)
(module+ test
(require typed/rackunit))
@ -190,6 +191,21 @@
,(pvλ (x y) (cast (max x y) (U Zero One)))))
'((0 0 0 0) (0 1 0 1) (1 0 0 1) (1 1 1 1)))))
(: table->function/list (All (a) (-> (Listof (Listof a))
(-> (Listof a) a))))
(define (table->function/list table)
(define ht-tab
(for/hash ([line (in-list table)]) : (HashTable (Listof a) a)
(define-values (x fx) (split-at-right line 1))
(values x (car fx))))
(λ (x) (hash-ref ht-tab x)))
(module+ test
(test-case "table->function/list"
(define negation/list (table->function/list '((#t #f) (#f #t))))
(check-true (negation/list '(#f)))
(check-false (negation/list '(#t)))))
(module untyped racket
(module+ test
(require rackunit))
@ -270,7 +286,8 @@
tabulate* tabulate*/strict tabulate*/pv
tabulate tabulate/strict tabulate/pv
tabulate*/pv/boolean tabulate/pv/boolean
tabulate*/pv/01 tabulate/pv/01)
tabulate*/pv/01 tabulate/pv/01
table->function/list)
(require (rename-in (submod 'typed untyped)
[tabulate tabulate/untyped]
@ -283,7 +300,6 @@
;; Functions
(contract-out
[table->function (-> (listof (*list/c any/c any/c)) procedure?)]
[table->function/list (-> (listof (*list/c any/c any/c)) procedure?)]
[enumerate-boolean-tables (-> number? (stream/c (listof (*list/c boolean? boolean?))))]
[enumerate-boolean-functions (-> number? (stream/c procedure?))]
[enumerate-boolean-functions/list (-> number? (stream/c procedure?))]
@ -338,20 +354,6 @@
(check-true (negation #f))
(check-false (negation #t))))
;;; Like table->function, but the produced function accepts a single
;;; list of arguments instead of individual arguments.
(define (table->function/list table)
((curry hash-ref)
(for/hash ([line table])
(let-values ([(x fx) (split-at-right line 1)])
(values x (car fx))))))
(module+ test
(test-case "table->function/list"
(define negation/list (table->function/list '((#t #f) (#f #t))))
(check-true (negation/list '(#f)))
(check-false (negation/list '(#t)))))
;;; Returns the stream of the truth tables of all Boolean functions of
;;; a given arity.
;;;

21
scribblings/functions.scrbl
View file

@ -240,6 +240,27 @@ Like @racket[tabulate/pv/01], but takes a list of functions of the same arity.
@section{Constructing functions}
@defproc[(table->function/list [table (Listof (Listof a))])
(-> (Listof a) a)]{
Given a table like the one produced by the functions of the @racket[tabulate]
family, creates a function which has this behaviour.
More precisely, given a line of @racket[table] without its last element, the
function returned by @racket[table->function/list] produces the corresponding
last element.
@examples[#:eval functions-evaluator
(define tab : (Listof (Listof Boolean))
'((#f #f #f)
(#f #t #f)
(#t #f #f)
(#t #t #t)))
(define and/list (table->function/list tab))
(and/list '(#f #t))
(and/list '(#t #t))
]}
@section{Random functions}
@section{Threshold Boolean functions}