From c6b7e19892fd1fa6be88dd72404c8428c796d582 Mon Sep 17 00:00:00 2001
From: giles <giles.bradshaw@rose-ash.com>
Date: Fri, 24 Apr 2026 19:07:31 +0000
Subject: [PATCH] lua: io stub (buffered) + print/tostring/tonumber +12 tests

---
 lib/lua/runtime.sx | 109 +++++++++++++++++++++++++++++++++++++++++++++
 lib/lua/test.sh    |  40 +++++++++++++++++
 plans/lua-on-sx.md |   4 +-
 3 files changed, 152 insertions(+), 1 deletion(-)

diff --git a/lib/lua/runtime.sx b/lib/lua/runtime.sx
index 1e13f01f..99a49521 100644
--- a/lib/lua/runtime.sx
+++ b/lib/lua/runtime.sx
@@ -1129,3 +1129,112 @@
 (dict-set! table "maxn" lua-table-maxn)
 
 (define unpack lua-unpack)
+
+;; ── io library (minimal stub — buffered; no real stdio) ───────
+(define io {})
+(define __io-buffer "")
+
+(define
+  lua-io-write
+  (fn (&rest args)
+    (begin
+      (define
+        loop
+        (fn (i)
+          (when (< i (len args))
+            (begin
+              (set! __io-buffer (str __io-buffer (lua-concat-coerce (nth args i))))
+              (loop (+ i 1))))))
+      (loop 0)
+      io)))
+
+(define
+  lua-io-read
+  (fn (&rest args) nil))
+
+(define
+  lua-io-open
+  (fn (&rest args) nil))
+
+(define
+  lua-io-lines
+  (fn (&rest args) (fn (&rest __) nil)))
+
+(define
+  lua-io-close
+  (fn (&rest args) true))
+
+(define
+  lua-io-flush
+  (fn (&rest args) nil))
+
+(define
+  lua-io-buffer
+  (fn ()
+    (let ((out __io-buffer))
+      (begin
+        (set! __io-buffer "")
+        out))))
+
+;; print(a, b, c) — args joined by tab, trailing newline
+(define
+  lua-print
+  (fn (&rest args)
+    (begin
+      (define
+        loop
+        (fn (i)
+          (when (< i (len args))
+            (begin
+              (when (> i 0) (set! __io-buffer (str __io-buffer "\t")))
+              (set! __io-buffer (str __io-buffer (lua-to-display (nth args i))))
+              (loop (+ i 1))))))
+      (loop 0)
+      (set! __io-buffer (str __io-buffer "\n"))
+      nil)))
+
+(define
+  lua-to-display
+  (fn (v)
+    (cond
+      ((= v nil) "nil")
+      ((= v true) "true")
+      ((= v false) "false")
+      ((= (type-of v) "string") v)
+      ((= (type-of v) "number") (str v))
+      ((= (type-of v) "dict") (str "table"))
+      ((or (= (type-of v) "function") (= (type-of v) "lambda")) "function")
+      (else (str v)))))
+
+(define
+  lua-tostring
+  (fn (v)
+    (cond
+      ((= (type-of v) "dict")
+        (let ((m (lua-get-mm v "__tostring")))
+          (cond
+            ((not (= m nil)) (lua-first (m v)))
+            (else (lua-to-display v)))))
+      (else (lua-to-display v)))))
+
+(define
+  lua-tonumber
+  (fn (&rest args)
+    (let ((v (first args))
+          (base (if (> (len args) 1) (nth args 1) nil)))
+      (cond
+        ((= (type-of v) "number") v)
+        ((= (type-of v) "string") (lua-to-number v))
+        (else nil)))))
+
+(dict-set! io "write" lua-io-write)
+(dict-set! io "read" lua-io-read)
+(dict-set! io "open" lua-io-open)
+(dict-set! io "lines" lua-io-lines)
+(dict-set! io "close" lua-io-close)
+(dict-set! io "flush" lua-io-flush)
+(dict-set! io "__buffer" lua-io-buffer)
+
+(define print lua-print)
+(define tostring lua-tostring)
+(define tonumber lua-tonumber)
diff --git a/lib/lua/test.sh b/lib/lua/test.sh
index 8566769a..92ca2d5f 100755
--- a/lib/lua/test.sh
+++ b/lib/lua/test.sh
@@ -832,6 +832,32 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 1341)
 (eval "(lua-eval-ast \"local t = {10, 20, 30, 40} local a, b = table.unpack(t, 2, 3) return a + b\")")
 
+;; ── Phase 6: io stub + print/tostring/tonumber ────────────────
+(epoch 1400)
+(eval "(lua-eval-ast \"io.write(\\\"hello\\\") return io.__buffer()\")")
+(epoch 1401)
+(eval "(lua-eval-ast \"io.write(\\\"a\\\", \\\"b\\\", \\\"c\\\") return io.__buffer()\")")
+(epoch 1402)
+(eval "(lua-eval-ast \"io.write(1, \\\" \\\", 2) return io.__buffer()\")")
+(epoch 1410)
+(eval "(lua-eval-ast \"print(\\\"x\\\", \\\"y\\\") return io.__buffer()\")")
+(epoch 1411)
+(eval "(lua-eval-ast \"print(1, 2, 3) return io.__buffer()\")")
+(epoch 1420)
+(eval "(lua-eval-ast \"return tostring(42)\")")
+(epoch 1421)
+(eval "(lua-eval-ast \"return tostring(nil)\")")
+(epoch 1422)
+(eval "(lua-eval-ast \"return tostring({})\")")
+(epoch 1430)
+(eval "(lua-eval-ast \"return tonumber(\\\"42\\\")\")")
+(epoch 1431)
+(eval "(lua-eval-ast \"if tonumber(\\\"abc\\\") == nil then return 1 else return 0 end\")")
+(epoch 1440)
+(eval "(lua-eval-ast \"if io.read() == nil then return 1 else return 0 end\")")
+(epoch 1441)
+(eval "(lua-eval-ast \"if io.open(\\\"x\\\") == nil then return 1 else return 0 end\")")
+
 EPOCHS
 
 OUTPUT=$(timeout 60 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
@@ -1249,6 +1275,20 @@ check 1331 "table.sort desc via cmp"        '301'
 check 1340 "unpack global"                  '60'
 check 1341 "table.unpack(t,i,j)"            '50'
 
+# ── Phase 6: io stub + print/tostring/tonumber ────────────────
+check 1400 "io.write single"                '"hello"'
+check 1401 "io.write multi strings"         '"abc"'
+check 1402 "io.write numbers + spaces"      '"1 2"'
+check 1410 "print two args tab-sep + NL"    '"x\ty\n"'
+check 1411 "print three ints"               '"1\t2\t3\n"'
+check 1420 "tostring(42)"                   '"42"'
+check 1421 "tostring(nil)"                  '"nil"'
+check 1422 "tostring({})"                   '"table"'
+check 1430 "tonumber(\"42\")"               '42'
+check 1431 "tonumber(\"abc\") → nil"        '1'
+check 1440 "io.read() → nil"                '1'
+check 1441 "io.open(x) → nil"               '1'
+
 TOTAL=$((PASS + FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "ok $PASS/$TOTAL Lua-on-SX tests passed"
diff --git a/plans/lua-on-sx.md b/plans/lua-on-sx.md
index 804bba48..ff6602de 100644
--- a/plans/lua-on-sx.md
+++ b/plans/lua-on-sx.md
@@ -71,7 +71,7 @@ Each item: implement → tests → tick box → update progress log.
 - [x] `string` — `format`, `sub`, `find`, `match`, `gmatch`, `gsub`, `len`, `rep`, `upper`, `lower`, `byte`, `char`
 - [x] `math` — full surface
 - [x] `table` — `insert`, `remove`, `concat`, `sort`, `unpack`
-- [ ] `io` — minimal stub (read/write to SX IO surface)
+- [x] `io` — minimal stub (read/write to SX IO surface)
 - [ ] `os` — time/date subset
 
 ### Phase 7 — modules + full conformance
@@ -82,6 +82,7 @@ Each item: implement → tests → tick box → update progress log.
 
 _Newest first. Agent appends on every commit._
 
+- 2026-04-24: lua: `io` stub + `print`/`tostring`/`tonumber` globals. io buffers to internal `__io-buffer` (tests drain it via `io.__buffer()`). print: tab-sep + NL. tostring respects `__tostring` metamethod. 334 tests.
 - 2026-04-24: lua: `table` lib — insert (append / at pos, shifts up), remove (last / at pos, shifts down), concat (sep, i, j), sort (insertion sort, optional cmp), unpack + table.unpack, maxn. Caught trap: local helper named `shift` collides with SX's `shift` special form → renamed to `tbl-shift-up`/`tbl-shift-down`. 322 tests.
 - 2026-04-24: lua: `math` lib — pi/huge + abs/ceil/floor/sqrt/exp/log/log10/pow/trig (sin/cos/tan/asin/acos/atan/atan2)/deg/rad/min/max (&rest)/fmod/modf/random (0/1/2 arg)/randomseed. Most ops delegate to SX primitives; log w/ base via change-of-base. 309 tests.
 - 2026-04-24: lua: `string` lib — len/upper/lower/rep/sub (1-idx + neg)/byte/char/find/match/gmatch/gsub/format. Patterns are literal-only (no `%d`/etc.); format is `%s`/`%d`/`%f`/`%%` only. `string.char` uses printable-ASCII lookup + tab/nl/cr. 292 tests.
@@ -108,6 +109,7 @@ _Shared-file issues that need someone else to fix. Minimal repro only._
 
 ## Known limitations (own code, not shared)
 
+- **`io` library is a stub** — `io.write`/`print` append to an internal `__io-buffer` (accessible via `io.__buffer()` which returns + clears it) instead of real stdout. `io.read`/`open`/`lines` return nil. Suitable for tests that inspect output; no actual stdio.
 - **`string.find`/`match`/`gmatch`/`gsub` patterns are LITERAL only** — no `%d`/`%a`/`.`/`*`/`+`/etc. Implementing Lua patterns is a separate work item; literal search covers the common case.
 - **`string.format`** supports only `%s`, `%d`, `%f`, `%%`. No width/precision flags (`%.2f`, `%5d`).
 - **`string.char`** supports printable ASCII 32–126 plus `\t`/`\n`/`\r`; other codes error.