diff options
Diffstat (limited to 'stlc-fix.rkt')
-rw-r--r-- | stlc-fix.rkt | 42 |
1 files changed, 21 insertions, 21 deletions
diff --git a/stlc-fix.rkt b/stlc-fix.rkt index cb6a592..e8f15e6 100644 --- a/stlc-fix.rkt +++ b/stlc-fix.rkt @@ -4,35 +4,35 @@ ;; The Simply-Typed Lambda Calculus, with general recursion ;; (interpret Expr Table[Sym, Expr]): Value -(define (interpret expr [Γ #hash()]) - (interpret- (strip (desugar expr)) Γ)) -(define (interpret- expr Γ) +(define (interpret expr) + (interpret-core (strip (desugar expr)) #hash())) +(define (interpret-core expr Γ) (match expr ['sole 'sole] [n #:when (natural? n) n] [x #:when (dict-has-key? Γ x) (dict-ref Γ x)] [`(fix ,e) - (match (interpret- e Γ) + (match (interpret-core e Γ) [`(λ ,x ,e ,env) ; FIXME: unsure what should be Γ and what should be env - (interpret- e (dict-set Γ x `(fix (λ ,x ,e ,Γ))))] + (interpret-core e (dict-set Γ x `(fix (λ ,x ,e ,Γ))))] [e (err (format "applying fix to unknown expression ~a" e))])] [`(λ ,id ,body) `(λ ,id ,body ,Γ)] [`(λ ,id ,body ,env) `(λ ,id ,body ,env)] [`(,body ,arg) - (match (interpret- body Γ) + (match (interpret-core body Γ) [`(λ ,id ,body ,env) - (interpret- body (dict-set env id (interpret- arg Γ)))] + (interpret-core body (dict-set env id (interpret-core arg Γ)))] [e (err (format "applying arg ~a to unknown expression ~a" arg e))])] [e (err (format "interpreting an unknown expression ~a" e))])) ;; (check Expr Type Table[Sym, Type]): Bool -(define (check expr with [Γ #hash()]) - (check- (desugar expr) with Γ)) -(define (check- expr with Γ) +(define (check expr with) + (check-core (desugar expr) with #hash())) +(define (check-core expr with Γ) (let ([with (if (dict-has-key? Γ with) (dict-ref Γ with) with)]) (match* (expr with) [('sole 'Unit) #t] @@ -41,22 +41,22 @@ (equal? (dict-ref Γ x) with)] [(`(fix ,e) with) - (check- (infer- e) `(,with → ,with) Γ)] + (check-core (infer-core e) `(,with → ,with) Γ)] [(`(λ (,x : ,t) ,e) `(,t1 → ,t2)) - (and (equal? t t1) (check- e t2 (dict-set Γ x t1)))] + (and (equal? t t1) (check-core e t2 (dict-set Γ x t1)))] [(`(,e1 ,e2) t) - (match (infer- e1 Γ) + (match (infer-core e1 Γ) [`(,t1 → ,t2) - (and (equal? t2 t) (equal? t1 (infer- e2 Γ)))] + (and (equal? t2 t) (equal? t1 (infer-core e2 Γ)))] [t #f])] [(e t) #f]))) ;; (infer Expr Table[Sym, Type]): Type -(define (infer expr [Γ #hash()]) - (infer- (desugar expr) Γ)) -(define (infer- expr Γ) +(define (infer expr) + (infer-core (desugar expr) #hash())) +(define (infer-core expr Γ) (match expr ['sole 'Unit] [n #:when (natural? n) 'Nat] @@ -64,16 +64,16 @@ (dict-ref Γ x)] [`(fix ,e) - (match (infer- e Γ) + (match (infer-core e Γ) [`(,t → ,t) t] [t (err (format "fix expects a term of type t → t, got ~a" t))])] [`(λ (,x : ,t) ,e) - `(,t → ,(infer- e (dict-set Γ x t)))] + `(,t → ,(infer-core e (dict-set Γ x t)))] [`(,e1 ,e2) - (match (infer- e1 Γ) + (match (infer-core e1 Γ) [`(,t1 → ,t2) - (if (check- e2 t1 Γ) t2 + (if (check-core e2 t1 Γ) t2 (err (format "inferred argument type ~a does not match arg ~a" t1 e2)))] [t (err (format "expected → type on application body, got ~a" t))])] |