lua: io stub (buffered) + print/tostring/tonumber +12 tests

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)