Brummel
e1587ebdae
First stdlib fn that imports three other stdlib modules (std_list,
std_either, std_pair) and returns a compound polymorphic ADT tree
(Pair<List<e>, List<a>>). Stresses monomorphisation across nested
parameterised ADTs.
What shipped:
- examples/std_either_list.{ailx,ail.json}: 3 combinators —
- lefts : forall e a. (List<Either<e, a>>) -> List<e>
- rights : forall e a. (List<Either<e, a>>) -> List<a>
- partition_eithers : forall e a. (List<Either<e, a>>)
-> Pair<List<e>, List<a>>
lefts/rights use depth-2 nested Ctor patterns (Cons (Left l) t)
— exercises 16a's desugar pass at a depth not reached by any
prior fixture.
- examples/std_either_list_demo.{ailx,ail.json}: drives all three
combinators on a five-element List<Either<Int, Int>>; expected
output one per line: 2, 3, 2, 3.
- crates/ail/tests/e2e.rs::std_either_list_demo: e2e count 34 → 35.
- docs/JOURNAL.md: Iter 15g entry.
Compiler bug surfaced (queued as 15g-aux, not fixed):
unify_for_subst in ailang-codegen/src/lib.rs accepts $u wildcards
only on the arg side. Mixing inline (Either Left n) and (Either
Right n) in a list literal lands $u on the param side via the
outer List<a>'s binding and errors. Reduced repro: `length [Left
1, Right 10]`. Demo works around with monomorphic mkleft/mkright
helpers; workaround documented inline. Fix is a one-line symmetric
extension of the early-return.
Tests: 94/94. Stdlib: 5 modules, 27 combinators.
47 lines
3.4 KiB
Plaintext
47 lines
3.4 KiB
Plaintext
; Iter 15g — fifth consumer demo. First demo to import four stdlib
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; modules (std_list, std_either, std_pair, std_either_list); first to
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; thread a List<Either<Int, Int>> through three combinators that
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; together exercise every monomorphisation site introduced by 15g.
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;
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; The list is constructed via the monomorphic helpers `mkleft` and
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; `mkright` rather than bare `(term-ctor std_either.Either Left ...)` /
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; `(term-ctor std_either.Either Right ...)`. This sidesteps a codegen
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; bug that 15g surfaced: when an inline list literal mixes
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; `Either Left n` (pins e, leaves a as `$u`) and `Either Right n` (pins
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; a, leaves e as `$u`), the synth-time unification of the outer
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; `List<a>`'s parameter against the `$u`-bearing element types fails
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; on the param side because `unify_for_subst` only accepts arg-side
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; `$u` wildcards. The helpers fully pin both type vars at the call
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; site, so each list element arrives with concrete `Either<Int, Int>`
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; and the bug is dodged. Logged as known-debt under 15g; the fix is
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; a one-line symmetric extension of the `$u` early-return.
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(module std_either_list_demo
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(import std_list)
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(import std_either)
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(import std_pair)
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(import std_either_list)
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(fn mkleft
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(doc "Monomorphic Left-injector at Either<Int, Int>. Pins both type vars at the call site so the codegen synth doesn't leave a `$u` wildcard on the second var.")
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(type (fn-type (params (con Int)) (ret (con std_either.Either (con Int) (con Int)))))
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(params x)
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(body (term-ctor std_either.Either Left x)))
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(fn mkright
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(doc "Monomorphic Right-injector at Either<Int, Int>. Symmetric to mkleft.")
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(type (fn-type (params (con Int)) (ret (con std_either.Either (con Int) (con Int)))))
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(params x)
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(body (term-ctor std_either.Either Right x)))
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(fn main
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(doc "Drive lefts, rights, and partition_eithers on the same five-element List<Either<Int, Int>> (Left 1, Right 10, Left 2, Right 20, Right 30). Expected output (one per line): 2, 3, 2, 3.")
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(type (fn-type (params) (ret (con Unit)) (effects IO)))
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(params)
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(body
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(seq (do io/print_int (app std_list.length (app std_either_list.lefts (term-ctor std_list.List Cons (app mkleft 1) (term-ctor std_list.List Cons (app mkright 10) (term-ctor std_list.List Cons (app mkleft 2) (term-ctor std_list.List Cons (app mkright 20) (term-ctor std_list.List Cons (app mkright 30) (term-ctor std_list.List Nil)))))))))
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(seq (do io/print_int (app std_list.length (app std_either_list.rights (term-ctor std_list.List Cons (app mkleft 1) (term-ctor std_list.List Cons (app mkright 10) (term-ctor std_list.List Cons (app mkleft 2) (term-ctor std_list.List Cons (app mkright 20) (term-ctor std_list.List Cons (app mkright 30) (term-ctor std_list.List Nil)))))))))
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(seq (do io/print_int (app std_list.length (app std_pair.fst (app std_either_list.partition_eithers (term-ctor std_list.List Cons (app mkleft 1) (term-ctor std_list.List Cons (app mkright 10) (term-ctor std_list.List Cons (app mkleft 2) (term-ctor std_list.List Cons (app mkright 20) (term-ctor std_list.List Cons (app mkright 30) (term-ctor std_list.List Nil))))))))))
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(do io/print_int (app std_list.length (app std_pair.snd (app std_either_list.partition_eithers (term-ctor std_list.List Cons (app mkleft 1) (term-ctor std_list.List Cons (app mkright 10) (term-ctor std_list.List Cons (app mkleft 2) (term-ctor std_list.List Cons (app mkright 20) (term-ctor std_list.List Cons (app mkright 30) (term-ctor std_list.List Nil))))))))))))))))
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