40b5fb5f7e
Rewrite specs.md tuple/failable/pack/UFCS/grammar sections to the new syntax, update readme.md, and refresh stale tuple references in example header comments. Also fixes two pre-existing doc inaccuracies surfaced in review: drop the value-discarding `;` in the tuple-return examples, and correct the §13 function-type grammar production (optional param list + optional trailing `!` channel). Optional semantics unchanged. current/CHECKPOINT-LANG.md logs the cutover.
37 lines
1.4 KiB
Plaintext
37 lines
1.4 KiB
Plaintext
// Phase 6 — the canonical heterogeneous `map`, end to end. A pack-fn whose
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// return type `$R` is inferred from the mapper's closure return:
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// - `mapper: Closure(..sources.T) -> $R` types the lambda's params from the
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// projected pack element types, and its body (`a + b`) drives `$R`.
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// - `$R` is inferred at the call site from the lowered mapper's closure ret,
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// bound into the mono (`-> VL($R)` ⇒ `VL(i64)`, `Combined($R, ..)` ⇒
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// `Combined(i64, ..)`), and folded into the mangle.
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// - `.(..sources)` materializes the pack into the `Tuple(..VL(Ts))` field (per-element
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// erase) and `mapper(..sources.get)` projects+spreads; `xx c` erases the
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// generic-struct instance to `VL(i64)` via the generic impl's monomorphized
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// thunk.
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#import "modules/std.sx";
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VL :: protocol(T: Type) { get :: (self: *Self) -> T; }
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IntCell :: struct { v: i64; }
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impl VL(i64) for IntCell { get :: (self: *IntCell) -> i64 => self.v; }
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Combined :: struct($R: Type, ..$Ts: []Type) {
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sources: Tuple(..VL(Ts));
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value: $R;
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}
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impl VL($R) for Combined($R, ..$Ts) { get :: (self: *Combined) -> $R => self.value; }
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map :: (mapper: Closure(..sources.T) -> $R, ..sources: VL) -> VL($R) {
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c : Combined($R, ..sources.T) = ---;
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c.sources = .(..sources);
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c.value = mapper(..sources.get);
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return xx c;
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}
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main :: () -> i32 {
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r := map((a, b) => a + b, IntCell.{ v = 40 }, IntCell.{ v = 2 });
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print("{}\n", r.get()); // 42
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0
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}
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