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Revert "Tried removing "x", I don't like it"

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This reverts commit 184886461ef3c5d70f30ba63b7257963f99fb53f.
This commit is contained in:
Suzanne Soy 2021-03-15 03:32:36 +00:00
parent 734dc957e0
commit b2fbddcba0
1 changed files with 30 additions and 33 deletions
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63
envlang.rkt
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@ -298,22 +298,17 @@ location of expr current-continuation
#;(
;; Using first-class environments and lazy evaluations:
;; λ, env, get, push, drop are keywords
;; λ, env, χ, get, push, drop are keywords
;; v-env
v ::= (\ env e) ;; open term, expects an env to close the term
|| […] ;; env mapping from names to values
v ::= (\ env χ e) ;; open term, expects an env to close the term
|| […] ;; mapping from names to values
|| "str"
|| 0
|| get ;; env → key → value
|| push ;; env → key → value → env
|| drop ;; env → key → env
|| car
|| cdr
|| (list v ...)
|| get
|| push
|| pop
e ::= v
|| (@ e e)
|| env
|| (list e ...)
|| (@ e e e)
TODO: instead of ad-hoc var-to-string conversion, use a functional env
@ -323,32 +318,34 @@ TODO: instead of ad-hoc var-to-string conversion, use a functional env
=> environment′ redex′ continuation frames′
;; Primitive application
APP [E] (@ (\ env e) [E′]) …
=> [E′] e …
APP env=E, χ=X (@ (\ env χ e) v-env (\ env () e-arg)) …
=> env=v-env,χ=(\ env () e-arg) e …
;;---------------------------------------------------------------------------------------------------------------------------
;; Evaluation of sub-parts of a primitive application
APP-F [E] (@ e-f e-env) …
=> [E] e-f … [E],(@ _ e-env)
;; 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)
APP-ENV [E] (@ e-f e-env) …
=> [E] e-env … [E],(@ v-f _ )
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 _ )
;;---------------------------------------------------------------------------------------------------------------------------
;; 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) ...)) …
;; 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)) …
;; 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:
SUGAR-LAM env=E, χ=X (λ var-name e) …
=> env=E′, χ=X (#%app (#%app λ var-name) e) …
;; defaults to:
=> env=E′, χ=X (@ capture
(push env)
env
(λ env χ (@ (λ env χ e)
(add env "var-name" χ)
χ)))