# Step: CHAR-array `+` coverage + ISO ConvResults

Tag `v3-charcat-convresults`. Suite **139/139**; fixpoint **OK**
(image **2,156,095 bytes**).

## CHAR-array `+` (verified, test added)

String concatenation for `ARRAY OF CHAR` already worked end-to-end
from the earlier string work (`StrCompat` treats two 1-D `ARRAY OF
CHAR` as string-compatible; `QbeGen.StrCat` → `m2strcat`, and the
result is assigned by content copy). It simply had no test:

- `a + b` (both `ARRAY OF CHAR`),
- `a + "c"` / `"x" + a` (a single-char literal is a `CHAR` operand,
  via `DeclCharStr`),
- `a + a + a` (chained).

`t_charcat.mod` (exit 15) locks all four in.

Note: a single-character **string** literal is a `CHAR` in classic
Modula-2, so `b := "z"` into a `CHAR` array is 210; write `b := "zz"`
or assign `b[0] := "z"`. Concatenation accepts the `CHAR` form
directly (`a + "c"`).

## ISO `ConvResults`

`Conversions` now reports an ISO-style status instead of only a
`BOOLEAN`:

```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;
```

- `strAllRight` / `strOutOfRange` / `strWrongFormat` / `strEmpty`.
- `strOutOfRange` is detected **before** the 32-bit accumulate wraps
  (`v > (IntMax - d) DIV 10`), because V3 has no `VAL(LONGINT, int)`
  or long→int narrowing to use a wider accumulator.
- The BOOLEAN shortcuts are retained under new names —
  `IntVal`/`CardVal`/`RealVal` — since the `StrTo*` results changed
  type. (`ConvProg` and `Showcase14` were updated to them.)

`convresults_prog.mod` (exit 127) covers every status for
`StrToInt`/`StrToCard`/`StrToReal`.

## Tests

- `t_charcat.mod` (15): CHAR-array `+`.
- `convresults_prog.mod` (127): all `ConvResults` codes.
- `conv_prog.mod` / `showcase14.mod`: switched to `IntVal`/`RealVal`.

## Files

`stdlib/conversions.def`/`.mod`, `compiler/tests/{t_charcat,
convresults_prog,conv_prog,showcase14}.mod`, `compiler/run_tests.sh`,
`docs/features.md`.