# V3 step 5.3 — Math, WholeIO, input (done 2026-09-22)

Third stdlib landing. Suite 93/93 (50 run — incl. 4 trap-aborts,
4 sessions, 2 session-output, 2 session-input, 1 unit — + 43 reject).
LL(1)-clean, zero gm2 warnings.

## Math (`stdlib/math`)

Direct libm bindings via `EXTERNAL` (the routine names are valid
Modula-2 identifiers and match the C symbols): `sqrt`, `exp`, `ln`,
`sin`, `cos`, `arctan`, plus `fabs` exposed as `abs`, and the
constants `Pi` / `E`. REAL parameters/returns lower as QBE `d`.
Harness now links `-lm`.

`MathProg` → 12 (`sqrt(144.0) + sin(0.0)`).

## Input (`runtime/syslib/shim.c` + `SysIO`)

Shim additions `m2readchar` (fgetc), `m2readint` (whitespace-skipping
signed decimal). `SysIO` gains `ReadChar` / `ReadInt`; the harness
gains `expect_run_files_in` (pipes stdin). `ReadProg` reads two
integers and prints the sum → `42`.

## WholeIO (`stdlib/wholeio`)

Classic `WriteInt` / `WriteCard` / `ReadInt(VAR)` / `ReadCard(VAR)`
over the shim integer routines. `WholeIOProg` reads two ints and
prints their product → `42`.

## Notes

- External functions returning `CHAR`/`INTEGER` bind directly
  (`m2readchar() : CHAR`, `m2readint() : INTEGER`); a zero-parameter
  external call is `name()`.
- `math.def` REAL constants are emitted as globals flushed at
  `main` startup (existing REAL-const path), so `Math.Pi` loads
  correctly in clients.

## Deferred to 5.4+

`Files`, `Storage` / `SYSTEM` (`ALLOCATE`/`DEALLOCATE`, `ADDRESS`,
generic pointers — needs SYSTEM types), explicit external link
names, string escapes, `ReadString`. Traps still `$abort`.