# Session summary — 2026-09-29: CHAR-array `+`, ConvResults, CLASS lowering

Suite **142/142**; self-hosting fixpoint **OK**
(`bootstrap/fixpoint.sh`, image **2,188,065 bytes**). `master`, tree
clean except the user's uncommitted `compiler/toto.mod`.

Three features landed this session, each its own tagged step.

## Steps, tags and headline commits

| Step | Tag | Commit | What |
| --- | --- | --- | --- |
| CHAR-array `+` + ConvResults | `v3-charcat-convresults` | `5e2056f` | `ARRAY OF CHAR` concatenation test; ISO `ConvResults` |
| Clarion CLASS lowering | `v3-class-lowering` | `ed02804` | fields, methods, `THIS`, single inheritance |
| Showcase | `v3-showcase17` | `de27462` | the three together |

## 1. CHAR-array `+` (verified + tested)

String concatenation for `ARRAY OF CHAR` already worked end-to-end
from the earlier string work; it just had no test. `t_charcat.mod`
(15) now locks in `a + b`, `a + "c"`, `"x" + a` and `a + a + a`.

(Classic note: a single-character *string* literal is a `CHAR`, so
`b := "z"` into a CHAR array is 210 — use `b := "zz"`; the `+`
operator accepts the `CHAR` form directly.)

## 2. ISO `ConvResults`

`Conversions` now reports a status enumeration:

```modula-2
TYPE ConvResults = (strAllRight, strOutOfRange, strWrongFormat,
                    strEmpty);
PROCEDURE StrToInt (s : ARRAY OF CHAR; VAR n : INTEGER) : ConvResults;
PROCEDURE StrToCard(s : ARRAY OF CHAR; VAR n : CARDINAL): ConvResults;
PROCEDURE StrToReal(VAR s : ARRAY OF CHAR; VAR x : REAL): ConvResults;
```

Overflow is detected before the 32-bit accumulate wraps (V3 has no
`VAL(LONGINT, int)` or long→int narrowing). The BOOLEAN shortcuts
live on as `IntVal`/`CardVal`/`RealVal`.

## 3. Clarion CLASS lowering

Classes now **execute** (see `docs/summary_class-lowering.md` for the
full design):

- A class is a record for layout; single inheritance lays a child's
  fields after the parent's, and field lookups walk the parent chain.
- Each method has a hidden `THIS` `VAR` parameter, pushed as the
  current `WITH` base so bare field names mean `THIS^.field`.
- `obj.M(args)` binds statically with the receiver as the hidden
  first argument; a `CLASS IMPLEMENTATION` reuses the declared method
  symbol (matching call-site and definition uids).
- `VIRTUAL` is accepted but dispatches statically for now; bare
  sibling-method calls and a class `BEGIN` init body stay 230.

## 4. Showcase

`compiler/tests/showcase17.mod` (`Showcase17`, exit 42) ties them
together: a `Bounded` counter class (inheriting from `Counter`) driven
through its receiver, a value parsed with `ConvResults`, and a label
built by CHAR-array concatenation.

```
showcase17 total=42
```

## Tests (142, was 139)

New: `t_charcat` (15), `convresults_prog` (127), `t_classmethod` (7),
`t_classinherit` (7), `TClassDefProg` (8), `Showcase17` (42).
`conv_prog`/`showcase14` moved to `IntVal`/`RealVal`;
`t_classdef.mod` became `t_classdef.def` (a definition used by
`TClassDefProg`).

## Resume

```sh
cd .../m2compiler-V3
./bootstrap/fixpoint.sh                       # FIXPOINT OK
cd compiler && ./build.sh && ./run_tests.sh   # 142/142
```

## Remaining polish

- CLASS: `VIRTUAL` vtable dispatch, sibling-method calls, class init
  bodies.
- `VAL(LONGINT|REAL, x)` and long→int narrowing.
- `IOChan`-over-`Files` extras; deeper `Strings`/`Math`.