62 lines
2.2 KiB
Markdown
62 lines
2.2 KiB
Markdown
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# ANCP v1 – Reversible Mapping (P0 subset)
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Status: Preview (12.7‑C P0). Scope is the sugar subset already implemented and gated in 12.7‑B.
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Goals
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- Provide a clear, reversible mapping between Nyash sugar and canonical forms.
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- Make round‑trip (original → canonical → ANCP → canonical → original) predictable for the subset.
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Gating
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- Runtime sugar is gated by `NYASH_SYNTAX_SUGAR_LEVEL=basic|full`.
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- ANCP tools/nyfmt remain PoC/docs only at this stage.
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Subset Mappings
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- Pipeline `|>`
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- Nyash: `lhs |> f(a,b)` → Canonical: `f(lhs, a, b)`
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- Nyash: `lhs |> obj.m(a)` → Canonical: `obj.m(lhs, a)`
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- Round‑trip invariant: No change of call order or arity.
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- Safe Access `?.`
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- Nyash: `a?.b` → Canonical (peek): `peek a { null => null, else => a.b }`
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- Nyash: `a?.m(x)` → Canonical: `peek a { null => null, else => a.m(x) }`
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- Round‑trip invariant: No change of receivers/args; only the null guard appears.
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- Default `??`
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- Nyash: `a ?? b` → Canonical (peek): `peek a { null => b, else => a }`
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- Round‑trip invariant: Both branches preserved as‑is.
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- Range `..`
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- Nyash: `a .. b` → Canonical: `Range(a, b)`
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- Round‑trip invariant: Closed form preserved; no inclusive/exclusive change.
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- Compound Assign `+=, -=, *=, /=`
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- Nyash: `x += y` → Canonical: `x = x + y`（`x` は変数/フィールド）
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- Round‑trip invariant: Operator identity preserved; left target identical.
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Examples (Before / Canonical / Round‑Trip)
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1) Pipeline + Default
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```
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Before: data |> normalize() |> transform() ?? fallback
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Canonical: peek transform(normalize(data)) { null => fallback, else => transform(normalize(data)) }
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RoundTrip: data |> normalize() |> transform() ?? fallback
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```
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2) Safe Access Chain
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```
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Before: user?.profile?.name
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Canonical: peek user { null => null, else => peek user.profile { null => null, else => user.profile.name } }
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RoundTrip: user?.profile?.name
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```
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3) Range + Compound Assign
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```
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Before: i += 1; r = 1 .. 5
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Canonical: i = i + 1; r = Range(1, 5)
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RoundTrip: i += 1; r = 1 .. 5
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```
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Notes
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- Precise precedence handling is left to the parser; mappings assume already parsed trees.
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- Full ANCP compact tokens will be documented in a separate spec revision.
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