spec: floats milestone — Float as IEEE-754 binary64 primitive

docs/roadmap.md

@@ -33,23 +33,32 @@ work progresses.
 
 ## P0 — In flight
 
-- [x] **\[milestone\]** design-md-consolidation — `docs/DESIGN.md`
-  is now a state-only specification across four thematic sweeps
-  (history anchors out, REVERTED + migration plans out,
-  schema-SoT inversion + data-model hardening, workflow /
-  cross-reference cleanup). Closed 2026-05-10.
-  - context: `docs/specs/2026-05-10-design-md-consolidation.md`,
-    JOURNAL milestone-close entry of same date.
+- [~] **\[milestone\]** Floats — introduce `Float` as IEEE-754
+  binary64 primitive type. One float type only (no `f32`).
+  IEEE-conformant equality: `eq : Float → Float → Bool` returns
+  `false` for `NaN == NaN`; **no `Eq` instance** (the partiality
+  is real and surfaces through `Maybe`-shaped comparators rather
+  than through a lying total instance). `Ord` likewise partial:
+  `compare : Float → Float → Maybe Ordering`. Includes literal
+  syntax in Form-A + Surface, codegen for arithmetic ops,
+  conversions Int↔Float, and `Show`-style printing without the
+  typeclass machinery (the typeclass wiring lands in Post-22
+  Prelude).
+  - context: this conversation (2026-05-10) — Float status quo
+    was "documented as a primitive but never implemented";
+    `crates/ailang-core/src/canonical.rs:14` says "no floats".
 
 ## P1 — Next
 
 - [ ] **\[milestone\]** Post-22 Prelude — ship `Show` / `Eq` / `Ord`
-  with the four primitive instances (Int, Bool, Str, Float); rewire
-  `print` through `Show.show`. Originally queued as 22b.4 in the
-  typeclass milestone, kept on hold pending demand.
+  with the three total-orderable primitive instances (Int, Bool, Str);
+  rewire `print` through `Show.show`. Float gets `Show` but **not**
+  `Eq` / `Ord` (partial — see Floats milestone). Originally queued
+  as 22b.4 in the typeclass milestone, kept on hold pending demand.
   - context: JOURNAL 2026-05-09 ("JOURNAL queue")
-  - depends on: design-md-consolidation (touches DESIGN.md schema
-    sections that the consolidation will reshape)
+  - depends on: Floats (the partial-Eq/Ord story for Float must be
+    settled before the Prelude classes ship, so the Prelude can
+    decide what's instanced and what isn't)
 
 ## P2 — Medium-term