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Reasoned PHP

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@igorwhiletrue

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Use logic to run your programs backwards!

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Use logic to run your programs backwards!

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Reasoned PHP

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function appendᵒ($l, $s, $out) { return condᵉ([ [≡($l, []), ≡($s, $out)], [fresh_all(($a, $d, $res) ==> [ consᵒ($a, $d, $l), consᵒ($a, $res, $out), appendᵒ($d, $s, $res), ])], ]); }

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run٭($q ==> appendᵒ([1, 2, 3], [4, 5, 6], $q));

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((lambda (_.0) (list _.0 (list 'quote _.0))) '(lambda (_.0) (list _.0 (list 'quote _.0)))

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((lambda (_.0) (list 'quote (list _.0 (list 'quote _.0)))) '(lambda (_.0) (list 'quote (list _.0 (list 'quote _.0))))) ! ((lambda (_.0) (list 'quote (list _.0 (list 'quote _.0)))) '(lambda (_.0) (list 'quote (list _.0 (list 'quote _.0)))))

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µKanren (define (var c) (vector c)) (define (var? x) (vector? x)) (define (var=? x1 x2) (= (vector-ref x1 0) (vector-ref x2 0))) ! (define (walk u s) (let ((pr (and (var? u) (assp (lambda (v) (var=? u v)) s)))) (if pr (walk (cdr pr) s) u))) ! (define (ext-s x v s) `((,x . ,v) . ,s)) ! (define (== u v) (lambda (s/c) (let ((s (unify u v (car s/c)))) (if s (unit `(,s . ,(cdr s/c))) mzero)))) ! (define (unit s/c) (cons s/c mzero)) (define mzero '()) ! (define (unify u v s) (let ((u (walk u s)) (v (walk v s))) (cond ((and (var? u) (var? v) (var=? u v)) s) ((var? u) (ext-s u v s)) ((var? v) (ext-s v u s)) ((and (pair? u) (pair? v)) (let ((s (unify (car u) (car v) s))) (and s (unify (cdr u) (cdr v) s)))) (else (and (eqv? u v) s))))) (define (call/fresh f) (lambda (s/c) (let ((c (cdr s/c))) ((f (var c)) `(,(car s/c) . ,(+ c 1)))))) ! (define (disj g1 g2) (lambda (s/c) (mplus (g1 s/c) (g2 s/c)))) (define (conj g1 g2) (lambda (s/c) (bind (g1 s/c) g2))) ! (define (mplus $1 $2) (cond ((null? $1) $2) ((procedure? $1) (lambda () (mplus $2 ($1)))) (else (cons (car $1) (mplus (cdr $1) $2))))) ! (define (bind $ g) (cond ((null? $) mzero) ((procedure? $) (lambda () (bind ($) g))) (else (mplus (g (car $)) (bind (cdr $) g)))))

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References • Propositions as Types
 Philip Wadler • How to Replace Failure by a List of Successes
 Philip Wadler • µKanren
 Jason Hemann, Daniel Friedman • Quine Generation via Relational Interpreters
 William Byrd, Eric Holk, Daniel Friedman

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References • The Reasoned Schemer
 Daniel Friedman, William Byrd, Oleg Kiselyov • Clause and Effect
 William Clocksin • The Annotated Turing
 Charles Petzold • Code
 Charles Petzold

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Questions? • minikanren.org • github.com/clojure/core.logic • github.com/igorw/reasoned-php • @igorwhiletrue