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582 lines
17 KiB
Plaintext
582 lines
17 KiB
Plaintext
;; Haskell strict evaluator (Phase 2).
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;;
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;; Consumes the post-desugar core AST and produces SX values. Strict
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;; throughout — laziness and thunks are Phase 3.
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;;
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;; Value representation:
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;; numbers / strings / chars → raw SX values
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;; constructor values → tagged lists (con-name first)
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;; functions: closure / multifun → {:type "fn" :kind … …}
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;; constructor partials → {:type "con-partial" …}
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;; built-ins → {:type "builtin" …}
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;;
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;; Multi-clause top-level definitions are bundled into a single
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;; multifun keyed by name; arguments are gathered through currying
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;; until arity is reached, then each clause's pattern list is matched
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;; in order. Recursive let bindings work because the binding env is
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;; built mutably so closures captured during evaluation see the
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;; eventual full env.
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(define
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hk-dict-copy
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(fn
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(d)
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(let ((nd (dict)))
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(for-each
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(fn (k) (dict-set! nd k (get d k)))
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(keys d))
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nd)))
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;; ── Thunks (Phase 3 — laziness) ─────────────────────────────
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;; A thunk wraps an unevaluated AST plus the env in which it was
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;; created. The first call to `hk-force` evaluates the body, replaces
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;; the body with the cached value, and flips `forced`. Subsequent
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;; forces return the cached value directly.
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(define
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hk-mk-thunk
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(fn
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(body env)
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{:type "thunk" :body body :env env :forced false :value nil}))
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(define
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hk-is-thunk?
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(fn (v) (and (dict? v) (= (get v "type") "thunk"))))
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(define
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hk-force
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(fn
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(v)
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(cond
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((hk-is-thunk? v)
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(cond
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((get v "forced") (get v "value"))
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(:else
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(let
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((res (hk-force (hk-eval (get v "body") (get v "env")))))
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(dict-set! v "forced" true)
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(dict-set! v "value" res)
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res))))
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(:else v))))
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;; Recursive force — used at the test/output boundary so test
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;; expectations can compare against fully-evaluated structures.
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(define
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hk-deep-force
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(fn
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(v)
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(let ((fv (hk-force v)))
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(cond
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((not (list? fv)) fv)
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((empty? fv) fv)
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(:else (map hk-deep-force fv))))))
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;; ── Function value constructors ──────────────────────────────
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(define
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hk-mk-closure
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(fn
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(params body env)
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{:type "fn" :kind "closure" :params params :body body :env env}))
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(define
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hk-mk-multifun
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(fn
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(arity clauses env)
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{:type "fn" :kind "multi" :arity arity :clauses clauses :env env :collected (list)}))
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(define
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hk-mk-builtin
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(fn
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(name fn arity)
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{:type "builtin" :name name :fn fn :arity arity :collected (list)}))
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;; ── Apply a function value to one argument ──────────────────
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(define
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hk-apply
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(fn
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(f arg)
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(let ((f (hk-force f)))
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(cond
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((not (dict? f))
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(raise (str "apply: not a function value: " f)))
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((= (get f "type") "fn")
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(cond
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((= (get f "kind") "closure") (hk-apply-closure f arg))
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((= (get f "kind") "multi") (hk-apply-multi f arg))
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(:else (raise "apply: unknown fn kind"))))
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((= (get f "type") "con-partial") (hk-apply-con-partial f arg))
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((= (get f "type") "builtin") (hk-apply-builtin f arg))
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(:else (raise "apply: not a function dict"))))))
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(define
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hk-apply-closure
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(fn
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(cl arg)
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(let
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((params (get cl "params"))
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(body (get cl "body"))
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(env (get cl "env")))
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(cond
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((empty? params) (raise "apply-closure: no params"))
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(:else
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(let
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((p1 (first params)) (rest-p (rest params)))
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(let
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((env-after (hk-match p1 arg env)))
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(cond
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((nil? env-after)
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(raise "pattern match failure in lambda"))
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((empty? rest-p) (hk-eval body env-after))
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(:else
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(hk-mk-closure rest-p body env-after))))))))))
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(define
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hk-apply-multi
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(fn
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(mf arg)
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(let
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((arity (get mf "arity"))
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(clauses (get mf "clauses"))
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(env (get mf "env"))
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(collected (append (get mf "collected") (list arg))))
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(cond
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((< (len collected) arity)
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(assoc mf "collected" collected))
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(:else (hk-dispatch-multi clauses collected env))))))
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(define
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hk-dispatch-multi
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(fn
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(clauses args env)
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(cond
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((empty? clauses)
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(raise "non-exhaustive patterns in function definition"))
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(:else
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(let
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((c (first clauses)))
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(let
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((pats (first c)) (body (first (rest c))))
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(let
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((env-after (hk-match-args pats args env)))
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(cond
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((nil? env-after)
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(hk-dispatch-multi (rest clauses) args env))
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(:else (hk-eval body env-after))))))))))
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(define
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hk-match-args
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(fn
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(pats args env)
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(cond
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((empty? pats) env)
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(:else
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(let
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((res (hk-match (first pats) (first args) env)))
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(cond
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((nil? res) nil)
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(:else
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(hk-match-args (rest pats) (rest args) res))))))))
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(define
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hk-apply-con-partial
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(fn
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(cp arg)
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(let
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((name (get cp "name"))
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(arity (get cp "arity"))
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(args (append (get cp "args") (list arg))))
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(cond
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((= (len args) arity) (hk-mk-con name args))
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(:else (assoc cp "args" args))))))
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(define
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hk-apply-builtin
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(fn
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(b arg)
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(let
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((arity (get b "arity"))
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(collected (append (get b "collected") (list arg))))
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(cond
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((< (len collected) arity)
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(assoc b "collected" collected))
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(:else
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;; Built-ins are strict in all their arguments. Force each
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;; collected thunk before invoking the underlying SX fn.
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(apply
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(get b "fn")
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(map hk-force collected)))))))
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;; ── Bool helpers (Bool values are tagged conses) ────────────
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(define
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hk-truthy?
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(fn
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(v)
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(and (list? v) (not (empty? v)) (= (first v) "True"))))
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(define hk-true (hk-mk-con "True" (list)))
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(define hk-false (hk-mk-con "False" (list)))
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(define hk-of-bool (fn (b) (if b hk-true hk-false)))
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;; ── Core eval ───────────────────────────────────────────────
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(define
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hk-eval
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(fn
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(node env)
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(cond
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((not (list? node)) (raise (str "eval: not a list: " node)))
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((empty? node) (raise "eval: empty list node"))
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(:else
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(let
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((tag (first node)))
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(cond
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((= tag "int") (nth node 1))
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((= tag "float") (nth node 1))
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((= tag "string") (nth node 1))
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((= tag "char") (nth node 1))
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((= tag "var") (hk-eval-var (nth node 1) env))
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((= tag "con") (hk-eval-con-ref (nth node 1)))
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((= tag "neg")
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(- 0 (hk-force (hk-eval (nth node 1) env))))
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((= tag "if") (hk-eval-if node env))
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((= tag "let") (hk-eval-let (nth node 1) (nth node 2) env))
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((= tag "lambda")
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(hk-mk-closure (nth node 1) (nth node 2) env))
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((= tag "app")
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(hk-apply
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(hk-eval (nth node 1) env)
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(hk-mk-thunk (nth node 2) env)))
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((= tag "op")
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(hk-eval-op
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(nth node 1)
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(nth node 2)
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(nth node 3)
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env))
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((= tag "case")
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(hk-eval-case (nth node 1) (nth node 2) env))
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((= tag "tuple")
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(hk-mk-tuple
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(map (fn (e) (hk-eval e env)) (nth node 1))))
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((= tag "list")
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(hk-mk-list
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(map (fn (e) (hk-eval e env)) (nth node 1))))
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((= tag "sect-left")
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(hk-eval-sect-left (nth node 1) (nth node 2) env))
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((= tag "sect-right")
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(hk-eval-sect-right (nth node 1) (nth node 2) env))
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(:else
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(raise (str "eval: unknown node tag '" tag "'")))))))))
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(define
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hk-eval-var
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(fn
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(name env)
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(cond
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((has-key? env name) (get env name))
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((hk-is-con? name) (hk-eval-con-ref name))
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(:else (raise (str "unbound variable: " name))))))
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(define
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hk-eval-con-ref
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(fn
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(name)
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(let ((arity (hk-con-arity name)))
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(cond
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((nil? arity) (raise (str "unknown constructor: " name)))
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((= arity 0) (hk-mk-con name (list)))
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(:else
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{:type "con-partial" :name name :arity arity :args (list)})))))
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(define
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hk-eval-if
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(fn
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(node env)
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(let ((cv (hk-force (hk-eval (nth node 1) env))))
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(cond
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((hk-truthy? cv) (hk-eval (nth node 2) env))
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((and (list? cv) (= (first cv) "False"))
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(hk-eval (nth node 3) env))
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((= cv true) (hk-eval (nth node 2) env))
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((= cv false) (hk-eval (nth node 3) env))
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(:else (raise "if: condition is not Bool"))))))
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(define
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hk-extend-env-with-match!
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(fn
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(env match-env)
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(for-each
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(fn (k) (dict-set! env k (get match-env k)))
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(keys match-env))))
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(define
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hk-eval-let-bind!
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(fn
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(b env)
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(let ((tag (first b)))
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(cond
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((= tag "fun-clause")
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(let
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((name (nth b 1))
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(pats (nth b 2))
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(body (nth b 3)))
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(cond
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((empty? pats)
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(dict-set! env name (hk-eval body env)))
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(:else
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(dict-set! env name (hk-mk-closure pats body env))))))
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((or (= tag "bind") (= tag "pat-bind"))
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(let ((pat (nth b 1)) (body (nth b 2)))
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(let ((val (hk-eval body env)))
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(let ((res (hk-match pat val env)))
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(cond
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((nil? res)
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(raise "let: pattern bind failure"))
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(:else
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(hk-extend-env-with-match! env res)))))))
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(:else nil)))))
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(define
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hk-eval-let
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(fn
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(binds body env)
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(let ((new-env (hk-dict-copy env)))
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;; Pre-seed names for fn-clauses so closures see themselves
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;; (mutual recursion across the whole binding group).
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(for-each
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(fn (b)
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(cond
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((= (first b) "fun-clause")
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(dict-set! new-env (nth b 1) nil))
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((and
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(= (first b) "bind")
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(list? (nth b 1))
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(= (first (nth b 1)) "p-var"))
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(dict-set! new-env (nth (nth b 1) 1) nil))
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(:else nil)))
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binds)
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(for-each (fn (b) (hk-eval-let-bind! b new-env)) binds)
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(hk-eval body new-env))))
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(define
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hk-eval-case
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(fn
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(scrut alts env)
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(let ((sv (hk-force (hk-eval scrut env))))
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(hk-try-alts alts sv env))))
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(define
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hk-try-alts
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(fn
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(alts val env)
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(cond
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((empty? alts) (raise "case: non-exhaustive patterns"))
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(:else
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(let
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((alt (first alts)))
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(let
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((pat (nth alt 1)) (body (nth alt 2)))
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(let
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((res (hk-match pat val env)))
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(cond
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((nil? res) (hk-try-alts (rest alts) val env))
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(:else (hk-eval body res))))))))))
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(define
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hk-eval-op
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(fn
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(op left right env)
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(let
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((lv (hk-force (hk-eval left env)))
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(rv (hk-force (hk-eval right env))))
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(hk-binop op lv rv))))
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(define
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hk-list-append
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(fn
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(a b)
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(cond
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((and (list? a) (= (first a) "[]")) b)
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((and (list? a) (= (first a) ":"))
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(hk-mk-cons (nth a 1) (hk-list-append (nth a 2) b)))
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(:else (raise "++: not a list")))))
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(define
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hk-binop
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(fn
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(op lv rv)
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(cond
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((= op "+") (+ lv rv))
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((= op "-") (- lv rv))
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((= op "*") (* lv rv))
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((= op "/") (/ lv rv))
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((= op "==") (hk-of-bool (= lv rv)))
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((= op "/=") (hk-of-bool (not (= lv rv))))
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((= op "<") (hk-of-bool (< lv rv)))
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((= op "<=") (hk-of-bool (<= lv rv)))
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((= op ">") (hk-of-bool (> lv rv)))
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((= op ">=") (hk-of-bool (>= lv rv)))
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((= op "&&") (hk-of-bool (and (hk-truthy? lv) (hk-truthy? rv))))
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((= op "||") (hk-of-bool (or (hk-truthy? lv) (hk-truthy? rv))))
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((= op ":") (hk-mk-cons lv rv))
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((= op "++") (hk-list-append lv rv))
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(:else (raise (str "unknown operator: " op))))))
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(define
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hk-eval-sect-left
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(fn
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(op e env)
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;; (e op) = \x -> e op x — bind e once, defer the operator call.
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(let ((ev (hk-eval e env)))
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(let ((cenv (hk-dict-copy env)))
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(dict-set! cenv "__hk-sect-l" ev)
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(hk-mk-closure
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(list (list :p-var "__hk-sect-x"))
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(list
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:op
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op
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(list :var "__hk-sect-l")
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(list :var "__hk-sect-x"))
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cenv)))))
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(define
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hk-eval-sect-right
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(fn
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(op e env)
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(let ((ev (hk-eval e env)))
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(let ((cenv (hk-dict-copy env)))
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(dict-set! cenv "__hk-sect-r" ev)
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(hk-mk-closure
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(list (list :p-var "__hk-sect-x"))
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(list
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:op
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op
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(list :var "__hk-sect-x")
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(list :var "__hk-sect-r"))
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cenv)))))
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;; ── Top-level program evaluation ────────────────────────────
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(define
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hk-init-env
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(fn
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()
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(let ((env (dict)))
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(dict-set! env "otherwise" hk-true)
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(dict-set!
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env
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"error"
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(hk-mk-builtin
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"error"
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(fn (msg) (raise (str "*** Exception: " msg)))
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1))
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(dict-set!
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env
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"not"
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(hk-mk-builtin
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"not"
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(fn (b) (hk-of-bool (not (hk-truthy? b))))
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1))
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(dict-set!
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env
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"id"
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(hk-mk-builtin "id" (fn (x) x) 1))
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env)))
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(define
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hk-bind-decls!
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(fn
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(env decls)
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(let ((groups (dict)) (pat-binds (list)))
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;; Pass 1: collect fun-clause groups by name; collect pat-binds
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;; in source order. Pre-seed env so any name can already be
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;; looked up by closures built in pass 2.
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(for-each
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(fn (d)
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(cond
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((= (first d) "fun-clause")
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(let
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((name (nth d 1)))
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(dict-set!
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groups
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name
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(append
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(if
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(has-key? groups name)
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(get groups name)
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(list))
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(list (list (nth d 2) (nth d 3)))))
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(when
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(not (has-key? env name))
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(dict-set! env name nil))))
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((or (= (first d) "bind") (= (first d) "pat-bind"))
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(append! pat-binds d))
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(:else nil)))
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decls)
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;; Pass 2: install multifuns for arity > 0; mark 0-arity for
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;; pass 3. The mutable env means recursive references work.
|
|
(let ((zero-arity (list)))
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(for-each
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(fn (name)
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(let ((clauses (get groups name)))
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|
(let ((arity (len (first (first clauses)))))
|
|
(cond
|
|
((> arity 0)
|
|
(dict-set!
|
|
env
|
|
name
|
|
(hk-mk-multifun arity clauses env)))
|
|
(:else (append! zero-arity name))))))
|
|
(keys groups))
|
|
;; Pass 3: evaluate 0-arity bodies and pat-binds.
|
|
(for-each
|
|
(fn (name)
|
|
(let ((clauses (get groups name)))
|
|
(dict-set!
|
|
env
|
|
name
|
|
(hk-eval (first (rest (first clauses))) env))))
|
|
zero-arity)
|
|
(for-each
|
|
(fn (d)
|
|
(let ((pat (nth d 1)) (body (nth d 2)))
|
|
(let ((val (hk-eval body env)))
|
|
(let ((res (hk-match pat val env)))
|
|
(cond
|
|
((nil? res)
|
|
(raise "top-level pattern bind failure"))
|
|
(:else (hk-extend-env-with-match! env res)))))))
|
|
pat-binds))
|
|
env)))
|
|
|
|
(define
|
|
hk-eval-program
|
|
(fn
|
|
(ast)
|
|
(cond
|
|
((nil? ast) (raise "eval-program: nil ast"))
|
|
((not (list? ast)) (raise "eval-program: not a list"))
|
|
(:else
|
|
(do
|
|
(hk-register-program! ast)
|
|
(let ((env (hk-init-env)))
|
|
(let
|
|
((decls
|
|
(cond
|
|
((= (first ast) "program") (nth ast 1))
|
|
((= (first ast) "module") (nth ast 4))
|
|
(:else (raise "eval-program: bad shape")))))
|
|
(hk-bind-decls! env decls))))))))
|
|
|
|
;; ── Source-level convenience ────────────────────────────────
|
|
(define
|
|
hk-run
|
|
(fn
|
|
(src)
|
|
(let ((env (hk-eval-program (hk-core src))))
|
|
(cond
|
|
((has-key? env "main") (get env "main"))
|
|
(:else env)))))
|
|
|
|
(define
|
|
hk-eval-expr-source
|
|
(fn
|
|
(src)
|
|
(hk-deep-force (hk-eval (hk-core-expr src) (hk-init-env)))))
|