Brummel
5bb721178f
Post-audit downstream-LLM-author field test of the post-removal Form-A surface. 4 fresh real-world programs written from DESIGN.md + form_a.md + public examples only (no compiler source): running sum-of-squares accumulator (loop/recur → 385), grade cascade (let-threaded if → 4/2/0), Horner polynomial straight-line build-up (let-shadow chain → 73), multi-state bracket scanner threading (rest,depth,ok) by tail recursion → true/false. 0 bugs, 0 friction, 0 spec_gap, 4 working — every task clean and correct on the first try with only let/if/loop/recur; all parse|render|parse byte-identical; zero mut/var/assign tokens produced (a doc-faithful author did not reach for the removed construct). The closest-to-friction case (multi-state machine restates the full state tuple per tail-call) is correctly classified working, not a spec_gap: that explicit-dataflow cost is the local-reasoning pillar working as designed; mut's implicit cross-iteration persistence is exactly the failure class the removal eliminates. mut-keyword rejection is fail-closed with a diagnostic that enumerates the surviving forms (no tombstone, no-nostalgia, as spec'd). Removal thesis empirically CONFIRMED — mut was redundant with let/if/loop/recur in 100% of the fresh tasks. The remove-mut-var-assign milestone is fully ratified and CLOSED: spec+plan+iter, audit clean (architect [high] form_a.md fixed in .tidy, bench causally exonerated), fieldtest clean. Roadmap P0 flipped [~]→[x]; WhatsNew user-facing entry appended.
84 lines
3.0 KiB
Plaintext
84 lines
3.0 KiB
Plaintext
; Axis: a small streaming-feel state machine threading MORE THAN
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; ONE piece of state, updating only a SUBSET per branch.
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;
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; Scan a token stream (a recursive Int list; 1 = '(', 2 = ')',
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; 0 = any other token) and decide if the brackets are balanced.
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;
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; Imperative instinct (exactly what `mut` would invite):
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; depth = 0
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; ok = true
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; for t in stream:
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; if t == 1: depth = depth + 1 ; only depth changes
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; elif t == 2:
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; if depth == 0: ok = false ; only ok changes
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; else: depth = depth - 1 ; only depth changes
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; ; t == 0 -> neither changes
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; return ok && depth == 0
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;
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; Surviving-surface shape: a recursive scanner fn threading
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; (rest, depth, ok) — `loop`/`recur` cannot walk an ADT (it rebinds
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; positionally, there is no structural pattern in a recur), so the
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; stream traversal is ordinary tail recursion; the per-branch
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; "update a subset of the state" becomes "pass the unchanged values
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; through unchanged". This is the task that most stresses the
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; removal: an imperative author updates one variable and leaves the
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; others implicitly alone; here every recur must restate all three.
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;
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; balanced "(()())" -> true ; stream 1 1 2 1 2 2
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; balanced ")(" -> false ; stream 2 1
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; Expected stdout (per line): true, false
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(module remove-mut_4_bracket_scanner
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(data TokStream
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(doc "1='(' , 2=')' , 0=other.")
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(ctor Nil)
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(ctor Cons (con Int) (con TokStream)))
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(fn scan
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(doc "Thread (rest, depth, ok). Each arm updates a subset of state; the unchanged components must be restated in every tail call.")
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(type
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(fn-type
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(params (own (con TokStream)) (con Int) (con Bool))
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(ret (con Bool))))
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(params rest depth ok)
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(body
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(match rest
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(case (pat-ctor Nil)
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(if ok (app == depth 0) false))
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(case (pat-ctor Cons t more)
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(match t
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(case (pat-lit 1)
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(tail-app scan more (app + depth 1) ok))
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(case (pat-lit 2)
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(if (app == depth 0)
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(tail-app scan more depth false)
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(tail-app scan more (app - depth 1) ok)))
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(case _
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(tail-app scan more depth ok)))))))
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(fn balanced
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(type (fn-type (params (own (con TokStream))) (ret (con Bool))))
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(params s)
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(body (app scan s 0 true)))
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(fn main
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(type (fn-type (params) (ret (con Unit)) (effects IO)))
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(params)
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(body
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(seq
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(app print
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(app balanced
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(term-ctor TokStream Cons 1
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(term-ctor TokStream Cons 1
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(term-ctor TokStream Cons 2
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(term-ctor TokStream Cons 1
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(term-ctor TokStream Cons 2
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(term-ctor TokStream Cons 2
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(term-ctor TokStream Nil)))))))))
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(app print
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(app balanced
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(term-ctor TokStream Cons 2
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(term-ctor TokStream Cons 1
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(term-ctor TokStream Nil)))))))))
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