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Hygiene-by-default was already present: user operatives close over static-env and bind formals + body $define!s in (extend STATIC-ENV), caller's env untouched. $let evaluates values in caller env, binds in fresh child env, runs body there. $define-in! explicitly targets an env. Full scope-set / frame-stamp hygiene is research-grade and documented as deferred future work in the reflective API notes.
494 lines
17 KiB
Plaintext
494 lines
17 KiB
Plaintext
;; lib/kernel/runtime.sx — the operative–applicative substrate and the
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;; standard Kernel environment.
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;;
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;; Phase 3 supplied four user-visible combiners ($vau, $lambda, wrap,
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;; unwrap). Phase 4 fills out the rest of the R-1RK core: $if, $define!,
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;; $sequence, eval, make-environment, get-current-environment, plus
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;; arithmetic, equality, list/pair, and boolean primitives — enough to
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;; write factorial.
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;;
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;; The standard env is built by EXTENDING the base env, not replacing
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;; it. So `kernel-standard-env` includes everything from `kernel-base-env`.
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;;
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;; Public API
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;; (kernel-base-env) — Phase 3 combiners
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;; (kernel-standard-env) — Phase 4 standard environment
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(define
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knl-eparam-sentinel
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(fn
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(sym)
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(cond
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((= sym "_") :knl-ignore)
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((= sym "#ignore") :knl-ignore)
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(:else sym))))
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(define
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knl-formals-ok?
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(fn
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(formals)
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(cond
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((not (list? formals)) false)
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((= (length formals) 0) true)
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((string? (first formals)) (knl-formals-ok? (rest formals)))
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(:else false))))
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;; ── $vau ─────────────────────────────────────────────────────────
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(define
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kernel-vau-impl
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(fn
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(args dyn-env)
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(cond
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((not (= (length args) 3))
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(error "$vau: expects (formals env-param body)"))
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(:else
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(let
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((formals (first args))
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(eparam-raw (nth args 1))
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(body (nth args 2)))
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(cond
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((not (knl-formals-ok? formals))
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(error "$vau: formals must be a list of symbols"))
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((not (string? eparam-raw))
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(error "$vau: env-param must be a symbol"))
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(:else
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(kernel-make-user-operative
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formals
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(knl-eparam-sentinel eparam-raw)
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body
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dyn-env))))))))
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(define
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kernel-vau-operative
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(kernel-make-primitive-operative kernel-vau-impl))
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;; ── $lambda ──────────────────────────────────────────────────────
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(define
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kernel-lambda-impl
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(fn
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(args dyn-env)
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(cond
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((not (= (length args) 2))
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(error "$lambda: expects (formals body)"))
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(:else
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(let
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((formals (first args)) (body (nth args 1)))
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(cond
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((not (knl-formals-ok? formals))
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(error "$lambda: formals must be a list of symbols"))
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(:else
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(kernel-wrap
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(kernel-make-user-operative formals :knl-ignore body dyn-env)))))))))
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(define
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kernel-lambda-operative
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(kernel-make-primitive-operative kernel-lambda-impl))
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;; ── wrap / unwrap / predicates ───────────────────────────────────
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(define
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kernel-wrap-applicative
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(kernel-make-primitive-applicative
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(fn
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(args)
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(cond
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((not (= (length args) 1))
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(error "wrap: expects exactly 1 argument"))
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(:else (kernel-wrap (first args)))))))
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(define
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kernel-unwrap-applicative
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(kernel-make-primitive-applicative
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(fn
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(args)
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(cond
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((not (= (length args) 1))
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(error "unwrap: expects exactly 1 argument"))
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(:else (kernel-unwrap (first args)))))))
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(define
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kernel-operative?-applicative
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(kernel-make-primitive-applicative
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(fn (args) (kernel-operative? (first args)))))
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(define
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kernel-applicative?-applicative
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(kernel-make-primitive-applicative
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(fn (args) (kernel-applicative? (first args)))))
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(define
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kernel-base-env
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(fn
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()
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(let
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((env (kernel-make-env)))
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(kernel-env-bind! env "$vau" kernel-vau-operative)
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(kernel-env-bind! env "$lambda" kernel-lambda-operative)
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(kernel-env-bind! env "wrap" kernel-wrap-applicative)
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(kernel-env-bind! env "unwrap" kernel-unwrap-applicative)
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(kernel-env-bind! env "operative?" kernel-operative?-applicative)
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(kernel-env-bind! env "applicative?" kernel-applicative?-applicative)
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env)))
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;; ── $if / $define! / $sequence ───────────────────────────────────
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(define
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kernel-if-operative
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(kernel-make-primitive-operative
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(fn
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(args dyn-env)
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(cond
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((not (= (length args) 3))
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(error "$if: expects (condition then-expr else-expr)"))
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(:else
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(let
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((c (kernel-eval (first args) dyn-env)))
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(if
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c
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(kernel-eval (nth args 1) dyn-env)
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(kernel-eval (nth args 2) dyn-env))))))))
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(define
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kernel-define!-operative
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(kernel-make-primitive-operative
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(fn
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(args dyn-env)
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(cond
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((not (= (length args) 2))
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(error "$define!: expects (name expr)"))
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((not (string? (first args)))
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(error "$define!: name must be a symbol"))
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(:else
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(let
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((v (kernel-eval (nth args 1) dyn-env)))
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(kernel-env-bind! dyn-env (first args) v)
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v))))))
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(define
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kernel-sequence-operative
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(kernel-make-primitive-operative
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(fn
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(args dyn-env)
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(cond
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((or (nil? args) (= (length args) 0)) nil)
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((= (length args) 1) (kernel-eval (first args) dyn-env))
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(:else
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(begin
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(kernel-eval (first args) dyn-env)
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((get kernel-sequence-operative :impl) (rest args) dyn-env)))))))
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;; ── eval / make-environment / get-current-environment ───────────
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(define
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kernel-quote-operative
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(kernel-make-primitive-operative
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(fn
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(args dyn-env)
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(cond
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((not (= (length args) 1)) (error "$quote: expects 1 argument"))
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(:else (first args))))))
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(define
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kernel-eval-applicative
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(kernel-make-primitive-applicative
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(fn
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(args)
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(cond
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((not (= (length args) 2))
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(error "eval: expects (expr env)"))
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((not (kernel-env? (nth args 1)))
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(error "eval: second arg must be a kernel env"))
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(:else (kernel-eval (first args) (nth args 1)))))))
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(define
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kernel-make-environment-applicative
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(kernel-make-primitive-applicative
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(fn
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(args)
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(cond
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((= (length args) 0) (kernel-make-env))
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((= (length args) 1)
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(cond
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((not (kernel-env? (first args)))
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(error "make-environment: parent must be a kernel env"))
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(:else (kernel-extend-env (first args)))))
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(:else (error "make-environment: 0 or 1 argument"))))))
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;; ── arithmetic and comparison (binary; trivial to extend later) ─
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(define
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kernel-get-current-env-operative
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(kernel-make-primitive-operative
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(fn
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(args dyn-env)
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(cond
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((not (= (length args) 0))
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(error "get-current-environment: expects 0 arguments"))
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(:else dyn-env)))))
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(define
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knl-bin-app
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(fn
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(name f)
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(kernel-make-primitive-applicative
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(fn
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(args)
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(cond
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((not (= (length args) 2))
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(error (str name ": expects 2 arguments")))
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(:else (f (first args) (nth args 1))))))))
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;; ── list / pair primitives ──────────────────────────────────────
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(define
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knl-unary-app
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(fn
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(name f)
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(kernel-make-primitive-applicative
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(fn
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(args)
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(cond
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((not (= (length args) 1))
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(error (str name ": expects 1 argument")))
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(:else (f (first args))))))))
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(define kernel-cons-applicative (knl-bin-app "cons" (fn (a b) (cons a b))))
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(define
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kernel-car-applicative
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(knl-unary-app
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"car"
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(fn
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(xs)
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(cond
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((or (nil? xs) (and (list? xs) (= (length xs) 0)))
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(error "car: empty list"))
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(:else (first xs))))))
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(define
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kernel-cdr-applicative
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(knl-unary-app
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"cdr"
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(fn
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(xs)
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(cond
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((or (nil? xs) (and (list? xs) (= (length xs) 0)))
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(error "cdr: empty list"))
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(:else (rest xs))))))
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(define
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kernel-list-applicative
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(kernel-make-primitive-applicative (fn (args) args)))
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(define
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kernel-length-applicative
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(knl-unary-app "length" (fn (xs) (length xs))))
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(define
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kernel-null?-applicative
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(knl-unary-app
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"null?"
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(fn (v) (or (nil? v) (and (list? v) (= (length v) 0))))))
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;; ── boolean / equality ──────────────────────────────────────────
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(define
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kernel-pair?-applicative
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(knl-unary-app
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"pair?"
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(fn (v) (and (list? v) (> (length v) 0)))))
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(define kernel-not-applicative (knl-unary-app "not" (fn (v) (not v))))
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(define kernel-eq?-applicative (knl-bin-app "eq?" (fn (a b) (= a b))))
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;; ── the standard environment ────────────────────────────────────
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(define
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kernel-equal?-applicative
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(knl-bin-app "equal?" (fn (a b) (= a b))))
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;; ── Encapsulations: Kernel's opaque-type idiom ──────────────────
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;;
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;; (make-encapsulation-type) → (encapsulator predicate decapsulator)
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;;
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;; Each call returns three applicatives over a fresh family identity.
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;; - (encapsulator V) → an opaque wrapper around V.
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;; - (predicate V) → true iff V was wrapped by THIS family.
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;; - (decapsulator W) → the inner value; errors on wrong family.
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;;
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;; Family identity is a fresh empty dict; SX compares dicts by reference,
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;; so two `(make-encapsulation-type)` calls return distinct families.
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;;
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;; Pattern usage (Phase 5 lacks destructuring, so accessors are explicit):
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;; ($define! triple (make-encapsulation-type))
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;; ($define! wrap-promise (car triple))
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;; ($define! promise? (car (cdr triple)))
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;; ($define! unwrap-promise (car (cdr (cdr triple))))
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(define kernel-make-encap-type-impl
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(fn (args)
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(cond
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((not (= (length args) 0))
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(error "make-encapsulation-type: expects 0 arguments"))
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(:else
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(let ((family {}))
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(let ((encap
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(kernel-make-primitive-applicative
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(fn (vargs)
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(cond
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((not (= (length vargs) 1))
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(error "encapsulator: expects 1 argument"))
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(:else
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{:knl-tag :encap
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:family family
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:value (first vargs)})))))
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(pred
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(kernel-make-primitive-applicative
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(fn (vargs)
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(cond
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((not (= (length vargs) 1))
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(error "predicate: expects 1 argument"))
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(:else
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(let ((v (first vargs)))
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(and (dict? v)
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(= (get v :knl-tag) :encap)
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(= (get v :family) family))))))))
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(decap
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(kernel-make-primitive-applicative
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(fn (vargs)
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(cond
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((not (= (length vargs) 1))
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(error "decapsulator: expects 1 argument"))
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(:else
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(let ((v (first vargs)))
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(cond
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((not (and (dict? v)
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(= (get v :knl-tag) :encap)))
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(error "decapsulator: not an encapsulation"))
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((not (= (get v :family) family))
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(error "decapsulator: wrong family"))
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(:else (get v :value))))))))))
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(list encap pred decap)))))))
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(define kernel-make-encap-type-applicative
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(kernel-make-primitive-applicative kernel-make-encap-type-impl))
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;; ── Hygiene: $let, $define-in!, make-environment ────────────────
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;;
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;; Kernel-on-SX is hygienic *by default* because user-defined operatives
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;; (Phase 3) bind their formals + any $define! in a CHILD env extending
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;; the operative's static-env, never the dyn-env. The caller's env is
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;; only mutated when code explicitly says so (e.g. `(eval expr env-arg)`).
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;;
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;; Phase 6 adds two helpers that make the property easy to lean on:
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;;
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;; ($let ((NAME EXPR) ...) BODY)
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;; Evaluates each EXPR in the calling env, binds NAME in a fresh
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;; child env, evaluates BODY in that child env. NAMES don't leak.
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;;
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;; ($define-in! ENV NAME EXPR)
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;; Binds NAME=value-of-EXPR in the *specified* env, not the dyn-env.
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;; Useful for operatives that need to mutate a sandbox env without
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;; touching their caller's env.
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;;
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;; Shutt's full scope-set / frame-stamp hygiene (lifted symbols carrying
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;; provenance markers so introduced bindings can shadow without
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;; capturing) is research-grade and not implemented here. Notes for
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;; `lib/guest/reflective/hygiene.sx` candidate API below the std env.
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(define knl-bind-let-vals!
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(fn (local bindings dyn-env)
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(cond
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((or (nil? bindings) (= (length bindings) 0)) nil)
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(:else
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(let ((b (first bindings)))
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(cond
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((not (and (list? b) (= (length b) 2)))
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(error "$let: each binding must be (name expr)"))
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((not (string? (first b)))
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(error "$let: binding name must be a symbol"))
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(:else
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(begin
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(kernel-env-bind! local
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(first b)
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(kernel-eval (nth b 1) dyn-env))
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(knl-bind-let-vals! local (rest bindings) dyn-env)))))))))
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(define kernel-let-operative
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(kernel-make-primitive-operative
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(fn (args dyn-env)
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(cond
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((not (= (length args) 2))
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(error "$let: expects (bindings body)"))
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((not (list? (first args)))
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(error "$let: bindings must be a list"))
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(:else
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(let ((local (kernel-extend-env dyn-env)))
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(knl-bind-let-vals! local (first args) dyn-env)
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(kernel-eval (nth args 1) local)))))))
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(define kernel-define-in!-operative
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(kernel-make-primitive-operative
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(fn (args dyn-env)
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(cond
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((not (= (length args) 3))
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(error "$define-in!: expects (env-expr name expr)"))
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((not (string? (nth args 1)))
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(error "$define-in!: name must be a symbol"))
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(:else
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(let ((target (kernel-eval (first args) dyn-env)))
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(cond
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((not (kernel-env? target))
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(error "$define-in!: first arg must evaluate to an env"))
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(:else
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(let ((v (kernel-eval (nth args 2) dyn-env)))
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(kernel-env-bind! target (nth args 1) v)
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v)))))))))
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(define
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kernel-standard-env
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(fn
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()
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(let
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((env (kernel-base-env)))
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(kernel-env-bind! env "$if" kernel-if-operative)
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(kernel-env-bind! env "$define!" kernel-define!-operative)
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(kernel-env-bind! env "$sequence" kernel-sequence-operative)
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(kernel-env-bind! env "$quote" kernel-quote-operative)
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(kernel-env-bind! env "eval" kernel-eval-applicative)
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(kernel-env-bind!
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env
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"make-environment"
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kernel-make-environment-applicative)
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(kernel-env-bind!
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env
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"get-current-environment"
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kernel-get-current-env-operative)
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(kernel-env-bind! env "+" (knl-bin-app "+" (fn (a b) (+ a b))))
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(kernel-env-bind! env "-" (knl-bin-app "-" (fn (a b) (- a b))))
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(kernel-env-bind! env "*" (knl-bin-app "*" (fn (a b) (* a b))))
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(kernel-env-bind! env "/" (knl-bin-app "/" (fn (a b) (/ a b))))
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(kernel-env-bind! env "<" (knl-bin-app "<" (fn (a b) (< a b))))
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(kernel-env-bind! env ">" (knl-bin-app ">" (fn (a b) (> a b))))
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(kernel-env-bind! env "<=?" (knl-bin-app "<=?" (fn (a b) (<= a b))))
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(kernel-env-bind! env ">=?" (knl-bin-app ">=?" (fn (a b) (>= a b))))
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(kernel-env-bind! env "=?" kernel-eq?-applicative)
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(kernel-env-bind! env "equal?" kernel-equal?-applicative)
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(kernel-env-bind! env "eq?" kernel-eq?-applicative)
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(kernel-env-bind! env "cons" kernel-cons-applicative)
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(kernel-env-bind! env "car" kernel-car-applicative)
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(kernel-env-bind! env "cdr" kernel-cdr-applicative)
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(kernel-env-bind! env "list" kernel-list-applicative)
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(kernel-env-bind! env "length" kernel-length-applicative)
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(kernel-env-bind! env "null?" kernel-null?-applicative)
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(kernel-env-bind! env "pair?" kernel-pair?-applicative)
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(kernel-env-bind! env "not" kernel-not-applicative)
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(kernel-env-bind! env "make-encapsulation-type"
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kernel-make-encap-type-applicative)
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(kernel-env-bind! env "$let" kernel-let-operative)
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(kernel-env-bind! env "$define-in!" kernel-define-in!-operative)
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||
env)))
|