haskell: real IO monad — putStrLn/print/putStr + hk-run-io (+10 tests, 575/575)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/haskell/tests/program-io.sx

@@ -0,0 +1,49 @@
+;; program-io.sx — tests for real IO monad (putStrLn, print, putStr).
+
+(hk-test
+  "putStrLn single line"
+  (hk-run-io "main = putStrLn \"hello\"")
+  (list "hello"))
+
+(hk-test
+  "putStrLn two lines via do"
+  (hk-run-io "main = do { putStrLn \"a\"; putStrLn \"b\" }")
+  (list "a" "b"))
+
+(hk-test "print Int" (hk-run-io "main = print 42") (list "42"))
+
+(hk-test "print Bool True" (hk-run-io "main = print True") (list "True"))
+
+(hk-test
+  "putStr collects string"
+  (hk-run-io "main = putStr \"hello\"")
+  (list "hello"))
+
+(hk-test
+  "do with let then putStrLn"
+  (hk-run-io "main = do\n  let s = \"world\"\n  putStrLn s")
+  (list "world"))
+
+(hk-test
+  "do sequence three lines"
+  (hk-run-io "main = do { putStrLn \"1\"; putStrLn \"2\"; putStrLn \"3\" }")
+  (list "1" "2" "3"))
+
+(hk-test
+  "print computed value"
+  (hk-run-io "main = print (6 * 7)")
+  (list "42"))
+
+(hk-test
+  "putStrLn returns IO unit"
+  (hk-deep-force (hk-run "main = putStrLn \"hi\""))
+  (list "IO" (list "Tuple")))
+
+(hk-test
+  "hk-run-io resets between calls"
+  (begin
+    (hk-run-io "main = putStrLn \"first\"")
+    (hk-run-io "main = putStrLn \"second\""))
+  (list "second"))
+
+{:fails hk-test-fails :pass hk-test-pass :fail hk-test-fail}