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.
39 lines
1.4 KiB
Plaintext
39 lines
1.4 KiB
Plaintext
// Feature 1 — TYPE-position pack projection `xs.T`. The per-element protocol
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// type-arg `T` projects into a Pack of types, usable in type/signature
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// positions: a tuple type `Tuple(..xs.T)` and a closure signature
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// `Closure(..xs.T) -> R`. (`T` of each element comes from its
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// `impl Box(T) for <elem>`.)
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#import "modules/std.sx";
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Box :: protocol(T: Type) {
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get :: (self: *Self) -> T;
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}
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IntCell :: struct { v: i64; }
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StrCell :: struct { s: string; }
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Dbl :: struct { n: i64; }
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impl Box(i64) for IntCell { get :: (self: *IntCell) -> i64 => self.v; }
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impl Box(string) for StrCell { get :: (self: *StrCell) -> string => self.s; }
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impl Box(i64) for Dbl { get :: (self: *Dbl) -> i64 => self.n * 2; }
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// Tuple type `Tuple(..xs.T)` — heterogeneous (i64, string), matched by the
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// value-projection `.(..xs.get)`.
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snap :: (..xs: Box) -> void {
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t : Tuple(..xs.T) = .(..xs.get);
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print("0={} 1={}\n", t.0, t.1);
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}
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// Closure signature `Closure(..xs.T) -> i64` — here `Closure(i64, i64) -> i64`.
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// The closure literal's params are contextually typed from the projection.
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fold :: (..xs: Box) -> i64 {
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cb : Closure(..xs.T) -> i64 = (a, b) => a + b;
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return cb(xs[0].get(), xs[1].get());
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}
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main :: () -> i32 {
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snap(IntCell.{ v = 42 }, StrCell.{ s = "hi" }); // (i64, string)
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print("fold={}\n", fold(IntCell.{ v = 10 }, Dbl.{ n = 5 })); // 10 + 10 = 20
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0
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}
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