commit 734dc957e07d113ad57533fff42d91701908c0c1
parent 400f7bf47c74f8930aa77d68638be78b7ea4bb36
Author: Suzanne Soy <ligo@suzanne.soy>
Date: Mon, 15 Mar 2021 03:32:27 +0000
Tried removing "x", I don't like it
Diffstat:
| M | envlang.rkt | | | 65 | ++++++++++++++++++++++++++++++++++------------------------------- |
1 file changed, 34 insertions(+), 31 deletions(-)
diff --git a/envlang.rkt b/envlang.rkt
@@ -298,17 +298,22 @@ location of expr current-continuation
#;(
;; Using first-class environments and lazy evaluations:
- ;; λ, env, χ, get, push, drop are keywords
+ ;; λ, env, get, push, drop are keywords
;; v-env
- v ::= (\ env χ e) ;; open term, expects an env to close the term
- || […] ;; mapping from names to values
+ v ::= (\ env e) ;; open term, expects an env to close the term
+ || […] ;; env mapping from names to values
|| "str"
|| 0
- || get
- || push
- || pop
+ || get ;; env → key → value
+ || push ;; env → key → value → env
+ || drop ;; env → key → env
+ || car
+ || cdr
+ || (list v ...)
e ::= v
- || (@ e e e)
+ || (@ e e)
+ || env
+ || (list e ...)
TODO: instead of ad-hoc var-to-string conversion, use a functional env
@@ -318,34 +323,32 @@ TODO: instead of ad-hoc var-to-string conversion, use a functional env
=> environment′ redex′ continuation frames′
;; Primitive application
- APP env=E, χ=X (@ (\ env χ e) v-env (\ env () e-arg)) …
- => env=v-env,χ=(\ env () e-arg) e …
+ APP [E] (@ (\ env e) [E′]) …
+ => [E′] e …
;;---------------------------------------------------------------------------------------------------------------------------
-;; Evaluation of sub-parts of an application
- APP-F env=E, χ=X (@ e-f e-env e-arg) …
- => env=E, χ=X e-f … [env=E,χ=X],(@ _ e-env e-arg)
+;; Evaluation of sub-parts of a primitive application
+ APP-F [E] (@ e-f e-env) …
+ => [E] e-f … [E],(@ _ e-env)
- APP-ENV env=E, χ=X (@ e-f e-env e-arg) …
- => env=E, χ=X e-env … [env=E,χ=X],(@ v-f _ e-arg)
-
- APP-ARG env=E, χ=X (@ e-f e-env e-arg) …
- => env=E, χ=X e-arg … [env=E,χ=X],(@ v-f v-env _ )
+ APP-ENV [E] (@ e-f e-env) …
+ => [E] e-env … [E],(@ v-f _ )
;;---------------------------------------------------------------------------------------------------------------------------
-;; Syntactic sugar (insertion of #%app)
- SUGAR-APP env=E, χ=X (#%app e-f e-arg ) …
- => env=E′, χ=X (@ (@ (get env "#%app")
- env
- (\ env () e-f))
- env
- (\ env () e-arg)) …
-;; defaults to:
- => env=E′, χ=X (@ e-f env (\ env () e-arg)) …
-
- SUGAR-LAM env=E, χ=X (λ var-name e) …
- => env=E′, χ=X (#%app (#%app λ var-name) e) …
-;; defaults to:
+;; Syntactic sugar (insertion of #%app for all parentheses that don't start with @)
+ SUGAR-APP [E] ( e-f e-arg ... ) …
+ => [E] (@ (@ (@ (@ get env) "#%app") …
+ (@ (@ (@ push env) "χ")
+ (list (\ env e-f) (\ env e-arg) ...))))
+;; where the default definition of #%app makes this reduce to:
+ => env=E′, χ=X (@ e-f env (list (\ env e-arg) ...)) …
+
+;; in particular, SUGAR-APP for lambda-expressions gives
+ SUGAR-APP env=E, χ=X (λ var-name e) …
+ => env=E′, χ=X (@ (@ (@ get env) "#%app")
+ (@ (@ (@ push env) "χ")
+ (list (\ env λ) (\ env var-name) (\ env e)))) …
+;; where the default definition of λ reduces to:
=> env=E′, χ=X (@ capture
- env
+ (push env)
(λ env χ (@ (λ env χ e)
(add env "var-name" χ)
χ)))
