mirror of
https://github.com/urbit/ares.git
synced 2024-11-26 09:57:56 +03:00
65 lines
3.1 KiB
Racket
65 lines
3.1 KiB
Racket
#lang racket
|
|
(define nock-eval
|
|
(lambda (nock)
|
|
(match nock
|
|
; Cell at head of formula, evaluate both formulae and return as cell
|
|
([cons (var a) (cons (cons (var b) (var c)) (var d))]
|
|
(cons
|
|
(nock-eval (cons a (cons b c)))
|
|
(nock-eval (cons a (cons d)))))
|
|
; literal tree index into subject
|
|
([cons (var a) (cons 0 b)] (nock-tree-find a b))
|
|
; literal
|
|
([cons _ (cons 1 b)] b)
|
|
; evaluate b with subject a
|
|
; evaluate c with subject a
|
|
; evaluate result of c with result of b as subject
|
|
([cons (var a) (cons 2 (cons (var b) (var c)))] (nock-eval (cons (nock-eval (cons a b)) (nock-eval (cons a c)))))
|
|
; evaluate b with a as subject, return
|
|
([cons (var a) (cons 3 (var b))] (if (pair? (nock-eval (cons a b))) 0 1))
|
|
([cons (var a) (cons 4 (var b))] (+ 1 (nock-eval (cons a b))))
|
|
([cons (var a) (cons 5 (cons (var b) (var c)))] (if (eqv? (nock-eval (cons a b) (cons a c))) 0 1))
|
|
; Here we deviate from slavishly following the spec to a symbolically-evaluated reduction of the spec
|
|
; Evaluate b with subject a. If 0 then evaluate c with subject a, else evaluate d with subject a
|
|
([cons (var a) (cons 6 (cons (var b) (cons (var c) (var d))))]
|
|
(let ([bval (nock-eval (cons a b))])
|
|
(if (= bval 0)
|
|
(nock-eval (cons a c))
|
|
(nock-eval (cons a d)))))
|
|
; Evaluate b with subject a, use result as subject and evaluate c
|
|
([cons (var a) (cons 7 (cons (var b) (var c)))] (nock-eval (cons (nock-eval (cons a b)) c)))
|
|
; Evaluate b with subject a, add result to subject a and evaluate c
|
|
([cons (var a) (cons 8 (cons (var b) (var c)))] (nock-eval (cons (cons (nock-eval (cons a b)) a) c)))
|
|
; Evaluate c with subject a to get a core, look up address b in the core and use it as a formula with the core
|
|
; as the subject
|
|
([cons (var a) (cons 9 (cons (var b) (var c)))]
|
|
(let ([core (nock-eval (cons a c))])
|
|
(nock-eval (cons core (nock-tree-find core b)))))
|
|
; Replace the address specified by b in the result of c with subject a with the result of d with subject a
|
|
([cons (var a) (cons 10 (cons (cons (var b) (var c)) (var d)))]
|
|
(nock-tree-edit (nock-eval a c) b (nock-eval a d)))
|
|
; Cell hint, compute then discard
|
|
([cons (var a) (cons 11 (cons (cons (var b) (var c)) (var d)))]
|
|
((const (nock-eval (cons b c))) (nock-eval (cons a d))))
|
|
; Atom hint, discard
|
|
([cons (var a) (cons 11 (cons _ (var c)))]
|
|
(nock-eval a c))
|
|
; Atom, return
|
|
([var a] a))))
|
|
|
|
; / operator in nock spec: tree addressing
|
|
(define nock-tree-find
|
|
(lambda (tree address)
|
|
(if (= address 1) tree
|
|
(nock-tree-find (if (even? address) (car tree) (cdr tree)) (quotient address 2)))))
|
|
|
|
; # operator in nock spec: tree editing
|
|
(define nock-tree-edit
|
|
(lambda (subtree address tree)
|
|
(if (= address 1) subtree
|
|
(if (even? address)
|
|
(cons (nock-tree-edit subtree (quotient address 2) (car tree)) (cdr tree))
|
|
(cons (car tree) (nock-tree-edit subtree (quotient address 2) (cdr tree)))))))
|
|
|
|
(nock-eval (cons (cons 2 3) (cons 0 3)))
|