giles
da27958d67
Extracted the data-half of Pratt-style precedence parsing: the operator table format and lookup. The climbing loop stays per-language because the two canaries use opposite conventions (lua: higher prec = tighter; prolog: lower prec = tighter, with xfx/xfy/yfx assoc tags) — forcing one shared loop adds callback indirection that obscures more than it shares. The brief's literal ask is "Grammar is a dict, not hardcoded cond" and that's what gets shared. Entry shape: (NAME PREC ASSOC). Three accessors: pratt-op-name / pratt-op-prec / pratt-op-assoc. One traversal: pratt-op-lookup. Ported lua/parser.sx — replaced 18-clause cond and the lua-binop-right? hardcoded `or` with a 15-entry lua-op-table, now queried via pratt-op-lookup. Ported prolog/parser.sx — pl-op-find (linear walk reimpl) deleted; pl-op-lookup wraps pratt-op-lookup; pl-token-op simplified to return the entry directly. Verification: - lua/test.sh: 185/185 = baseline. - prolog/conformance.sh: 590/590 = baseline (timestamp-only diff). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
29 lines
1.1 KiB
Plaintext
29 lines
1.1 KiB
Plaintext
;; lib/guest/pratt.sx — operator-table format + lookup for Pratt-style
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;; precedence climbing.
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;;
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;; The climbing loop stays per-language because the two canaries use
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;; opposite conventions (Lua: higher prec = tighter; Prolog: lower prec =
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;; tighter, with xfx/xfy/yfx assoc tags). Forcing a single loop adds
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;; callback indirection that obscures more than it shares.
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;;
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;; What IS shared and gets extracted: the operator-table format and lookup.
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;; "Grammar is a dict, not hardcoded cond."
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;;
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;; Entry shape: (NAME PREC ASSOC).
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;; NAME — string, the operator's source token.
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;; PREC — integer, in the host's own convention.
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;; ASSOC — :left | :right | :none for languages with traditional
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;; associativity, or "xfx" / "xfy" / "yfx" for Prolog-style.
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(define
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pratt-op-lookup
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(fn (table name)
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(cond
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((empty? table) nil)
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((= (first (first table)) name) (first table))
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(:else (pratt-op-lookup (rest table) name)))))
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(define pratt-op-name (fn (entry) (first entry)))
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(define pratt-op-prec (fn (entry) (nth entry 1)))
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(define pratt-op-assoc (fn (entry) (nth entry 2)))
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