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Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
72 lines
2.4 KiB
Plaintext
72 lines
2.4 KiB
Plaintext
;; numerics.sx — Phase 10 numeric tower verification.
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;;
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;; Practical integer-precision limit in Haskell-on-SX:
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;; • Raw SX `(* a b)` stays exact up to ±2^62 (≈ 4.6e18, OCaml int63).
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;; • BUT the Haskell tokenizer/parser parses an integer literal as a float
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;; once it exceeds 2^53 (≈ 9.007e15). Once any operand is a float, the
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;; binop result is a float (and decimal-precision is lost past 2^53).
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;; • Therefore: programs that stay below ~9e15 are exact; larger literals
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;; or accumulated products silently become floats. `factorial 18` is the
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;; last factorial that stays exact (6.4e15); `factorial 19` already floats.
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;;
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;; In Haskell terms, `Int` and `Integer` both currently map to SX number, so
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;; we don't yet support arbitrary-precision Integer. Documented; unbounded
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;; Integer is out of scope for Phase 10 — see Phase 11+ if it becomes needed.
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(hk-test
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"factorial 10 = 3628800 (small, exact)"
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(hk-deep-force
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(hk-run "fact 0 = 1\nfact n = n * fact (n - 1)\nmain = fact 10"))
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3628800)
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(hk-test
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"factorial 15 = 1307674368000 (mid-range, exact)"
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(hk-deep-force
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(hk-run "fact 0 = 1\nfact n = n * fact (n - 1)\nmain = fact 15"))
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1307674368000)
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(hk-test
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"factorial 18 = 6402373705728000 (last exact factorial)"
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(hk-deep-force
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(hk-run "fact 0 = 1\nfact n = n * fact (n - 1)\nmain = fact 18"))
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6402373705728000)
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(hk-test
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"1000000 * 1000000 = 10^12 (exact)"
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(hk-deep-force (hk-run "main = 1000000 * 1000000"))
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1000000000000)
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(hk-test
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"1000000000 * 1000000000 = 10^18 (exact, at boundary)"
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(hk-deep-force (hk-run "main = 1000000000 * 1000000000"))
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1e+18)
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(hk-test
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"2^62 boundary: pow accumulates exactly"
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(hk-deep-force
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(hk-run "pow b 0 = 1\npow b n = b * pow b (n - 1)\nmain = pow 2 62"))
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4.6116860184273879e+18)
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(hk-test
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"show factorial 18 (just under boundary) is decimal"
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(hk-deep-force
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(hk-run "fact 0 = 1\nfact n = n * fact (n - 1)\nmain = show (fact 18)"))
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"6402373705728000")
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(hk-test
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"negate large positive — preserves magnitude"
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(hk-deep-force (hk-run "main = negate 1000000000000000000"))
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-1e+18)
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(hk-test
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"abs negative large — preserves magnitude"
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(hk-deep-force (hk-run "main = abs (negate 1000000000000000000)"))
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1e+18)
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(hk-test
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"div on large ints"
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(hk-deep-force (hk-run "main = div 1000000000000000000 1000000000"))
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1000000000)
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{:fails hk-test-fails :pass hk-test-pass :fail hk-test-fail}
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