show renders to a string instead of printing

Examples/contracts.ikr

@@ -7,4 +7,4 @@
 (contract raw operative (any) any pure #t)
 
 (printf "double={0}\n" (double 21))
-(show (raw (+ 1 2)))
+(print (show (raw (+ 1 2))))

Examples/vau-dotnet.ikr

@@ -30,7 +30,7 @@
   (vau (exp) env
     (begin
       (write "  >> ")
-      (show exp)
+      (print (show exp))
       (writeln "")
       (eval exp env))))
 

Examples/zipper.ikr

@@ -21,7 +21,7 @@
 (define tree1 '(a (b) (c (d 1 2)) e))
 (define tree2 '(z (u) (v (w 10 12)) y))
 
-(depth-first (lambda (node) (begin (show node) (print "\n") #f)) tree1)
+(depth-first (lambda (node) (begin (print (show node)) (print "\n") #f)) tree1)
 
 (provide! (zipper zipper? z-curr-node z-k)
 
@@ -50,7 +50,7 @@
 				(if 
 					(zipper? x) 
 					(begin 
-						(show (z-curr-node x)) 
+						(print (show (z-curr-node x))) 
 						(print "\n") 
 						(loop ((z-k x) #f)))
 					#f))))

IronKernel.Runtime/Interop.fs

@@ -328,11 +328,12 @@
                         bounceContinue env cont Inert
           | _ -> signal cont (NumArgs(2,prms))
 
+        /// Render a value's printed representation as a string. Pure --
+        /// rendering grants no host authority, so `show` exists under every
+        /// profile; writing is `print`, `write`, and the ports' job. It used
+        /// to write to the console itself and return inert, which made the
+        /// natural `(print (show x))` an arity error on print.
         let show env cont (prms : LispVal list) =
           match prms with
-          | _ when not (has HostIO env) ->
-              signal cont (CapabilityDenied "host output requires HostIO")
-          | h :: _ ->
-              System.Console.Write(showVal h)
-              bounceContinue env cont Inert
-          | [] -> signal cont (NumArgs(1, []))
+          | [value] -> bounceContinue env cont (Obj(showVal value :> obj))
+          | _ -> signal cont (NumArgs(1, prms))

IronKernel.Runtime/Runtime.fs

@@ -2754,6 +2754,8 @@
                         Some(certifiedVariadicApplicative name [NumberShape; NumberShape] 2 NumberShape)
                     | "<" | "<=" | ">" ->
                         Some(certifiedApplicative name [NumberShape; NumberShape] BooleanShape)
+                    | "show" ->
+                        Some(certifiedApplicative name [AnyShape] StringShape)
                     | _ -> None
                 let value =
                     match contract with
@@ -2785,7 +2787,7 @@
                     (name <> "load" || Set.contains SourceLoading capabilities)
                     && (not (Set.contains name
                                 (Set.ofList
-                                    [ "print"; "printf"; "show"; "read"; "write"
+                                    [ "print"; "printf"; "read"; "write"
                                       "close-input-file"; "close-output-file"
                                       "get-current-input-port"; "get-current-output-port"
                                       "with-input-from-file"; "with-output-to-file"

IronKernel.Tests/CliTests.fs

@@ -669,3 +669,19 @@ let ``repl completion extends the symbol at the cursor`` () =
         // Control: a bare tab must not dump the whole environment.
         let _, none = completionCandidates env "(" 1
         Assert.Empty none
+
+[<Fact>]
+let ``print of show renders and writes -- the print-show regression`` () =
+    match bootstrapEnv () with
+    | Choice1Of2 error -> failwith (showError error)
+    | Choice2Of2 env ->
+        let original = Console.Out
+        use writer = new StringWriter()
+        Console.SetOut writer
+        try
+            match runSource env "print-show.ikr" "(print (show (list 1 2)))\n(print (show (list 3 4)))\n" with
+            | Choice1Of2 error -> failwith (showError error)
+            | Choice2Of2 _ -> ()
+        finally
+            Console.SetOut original
+        Assert.Equal("(1 2)(3 4)", writer.ToString())

IronKernel.Tests/InteropTests.fs

@@ -228,3 +228,26 @@ let ``CLR boolean results are Kernel booleans`` () =
         """(. System.Char IsDigit (. "x" get_Chars 0))""", Bool false
         """(.get System.Environment Is64BitProcess)""", Bool System.Environment.Is64BitProcess
     ]
+
+[<Fact>]
+let ``show renders a value to a string`` () =
+    evalSessionKernel [
+        "(show 5)", Obj "5"
+        "(show (list 1 2))", Obj "(1 2)"
+        // The idiom that used to fail: show wrote to the console itself and
+        // returned inert, so print then rejected #inert with an arity error.
+        "(print (show (list 1 2)))", Inert
+    ]
+
+[<Fact>]
+let ``show requires no authority`` () =
+    IronKernel.RuntimeSourceServices.configure ()
+    IronKernel.Compiler.installBodyCompiler ()
+    let env = makePrimitiveBindingsForProfile Minimal
+    match evalIn env "(show 42)" with
+    | Obj value -> Assert.Equal("42", string value)
+    | other -> failwithf "unexpected show result: %s" (showVal other)
+    // Control: writing is still authority the minimal profile lacks.
+    match evalIn env "(print \"x\")" with
+    | Status message -> Assert.Contains("print", message)
+    | other -> failwithf "print unexpectedly available: %s" (showVal other)

lib/IronKernel.Test/src/test.ikr

@@ -76,7 +76,7 @@
   (define show-line
     (lambda (label value)
       (printf "        {0} " label)
-      (show value)
+      (print (show value))
       (printf "\n")))
 
   ; --- checks -------------------------------------------------------------

website/docs/guide.html

@@ -314,7 +314,7 @@ <h2 id="diy">14. Invent your own syntax</h2>
           <pre><code>(define trace
   (vau (exp) env
     (begin
-      (show exp)
+      (print (show exp))
       (. System.Console WriteLine "")
       (eval exp env))))
 

website/docs/operators.html

@@ -470,7 +470,7 @@ <h2 id="io">I/O &amp; display</h2>
         <section class="op" id="op-print">
           <div class="op-head"><h3 class="op-name">print / printf / show</h3><span class="op-kind">applicative</span></div>
           <p class="op-sig">(print obj) (printf format arg…) (show value)</p>
-          <p><code>printf</code> uses .NET <code>String.Format</code> placeholders (<code>{0}</code>, <code>{1}</code>, …). <code>show</code> writes the Kernel printed representation.</p>
+          <p><code>printf</code> uses .NET <code>String.Format</code> placeholders (<code>{0}</code>, <code>{1}</code>, …). <code>show</code> renders the Kernel printed representation as a string — pure, available under every profile; write it with <code>(print (show value))</code>.</p>
         </section>
         <section class="op" id="op-ports">
           <div class="op-head"><h3 class="op-name">open-*-file / read / write / …</h3><span class="op-kind">applicative</span></div>