Executing code in v.5.2 kernel from within v.7.01 session through MathLink

I have Mathematica 7.01 and Mathematica 5.2 installed on the same machine. I wish to be able to evaluate code in the v.5.2 kernel from within Mathematica 7.01 session. I mean that running Mathematica 7.0.1 standard session I wish to have a command like kernel5Evaluate to evaluate some code in the 5.2 kernel and return the result into the 7.01 kernel and linked 7.01 FrontEnd notebook in such a way as this code would be executed in the 7.01 kernel.

For example (in the standard Mathematica v.7.01 session):

In[1]:= solutionFrom5 = kernel5Evaluate[NDSolve[{(y^\[Prime])[x]==y[x],y[1]==2},y,{x,0,3}]]
Out[1]= {{y -> InterpolatingFunction[{{0., 3.}}, <>]}}

In[2]:= kernel5Evaluate[Plot3D[Sin[x y],{x,-Pi,Pi},{y,-Pi,Pi}]]
During evaluation of In[2]:= GraphicsData["PostScript", "\<\.开发者_如何转开发...........
Out[2]= -SurfaceGraphics-

In the both cases the result should be as if the v.5.2 kernel is set to be "Notebook's Kernel" in the v.7.01 FrontEnd. And of course solutionFrom5 variable should be set to the real solution returned by v.5.2 kernel.

Here is an implementation based on Simon's code. It still requires improvement. The one unclear thing to me is how to handle Messages generated in the slave (v.5.2) kernel.

Here is my code:

Clear[linkEvaluate]
SetAttributes[linkEvaluate, HoldRest]
linkEvaluate[link_LinkObject, expr_] := Catch[
   Module[{out = {}, postScript = {}, packet, outputs = {}},
    While[LinkReadyQ[link], 
     Print["From the buffer:\t", LinkRead[link]]];
    LinkWrite[link, Unevaluated[EnterExpressionPacket[expr]]];
    While[Not@MatchQ[packet = LinkRead[link], InputNamePacket[_]],
     Switch[packet,
      DisplayPacket[_], AppendTo[postScript, First@packet],
      DisplayEndPacket[_], AppendTo[postScript, First@packet]; 
      CellPrint@
         Cell[GraphicsData["PostScript", #], "Output", 
          CellLabel -> "Kernel 5.2 PostScript ="] &@
       StringJoin[postScript]; postScript = {},
      TextPacket[_], 
      If[StringMatchQ[First@packet, 
        WordCharacter .. ~~ "::" ~~ WordCharacter .. ~~ ": " ~~ __], 
       CellPrint@
        Cell[BoxData@
          RowBox[{StyleBox["Kernel 5.2 Message = ", 
             FontColor -> Blue], First@packet}], "Message"], 
       CellPrint@
        Cell[First@packet, "Output", CellLabel -> "Kernel 5.2 Print"]],
      OutputNamePacket[_], AppendTo[outputs, First@packet];,
      ReturnExpressionPacket[_], AppendTo[outputs, First@packet];,
      _, AppendTo[out, packet]
      ]
     ];
    If[Length[out] > 0, Print[out]];
    Which[
     (l = Length[outputs]) == 0, Null,
     l == 2, Last@outputs,
     True, multipleOutput[outputs]
     ]
    ]];
Clear[kernel5Evaluate]
SetAttributes[kernel5Evaluate, HoldAll]
kernel5Evaluate[expr_] := 
 If[TrueQ[MemberQ[Links[], $kern5]], linkEvaluate[$kern5, expr], 
  Clear[$kern5]; $kern5 = LinkLaunch[
    "C:\\Program Files\\Wolfram Research\\Mathematica\\5.2\\MathKernel.exe -mathlink"]; 
  LinkRead[$kern5]; 
  LinkWrite[$kern5, 
   Unevaluated[EnterExpressionPacket[$MessagePrePrint = InputForm;]]];
   LinkRead[$kern5]; kernel5Evaluate[expr]]

Here are test expressions:

plot = kernel5Evaluate[Plot3D[Sin[x y], {x, 0, Pi}, {y, 0, Pi}]]
plot = kernel5Evaluate[Plot[Sin[x], {x, 0, Pi}]; Plot[Sin[x], {x, -Pi, Pi}]] // 
  DeleteCases[#, HoldPattern[DefaultFont :> $DefaultFont], Infinity] &
s = kernel5Evaluate[
  NDSolve[{y'[x] == y[x] Cos[x + y[x]], y[0] == 1}, y, {x, 0, 30}]]
s // InputForm // Short
kernel5Evaluate[1/0; Print["s"];]

It seems to work as expected. However it could be better...

Here is working implementation of what I wanted. I have added checking for a dead MathLink connection as suggested by Todd Gayley here. Now kernel5Evaluate works reliable even if the slave kernel was terminated in unusual way. I also have much improved parsing of Messages and added some diagnostic messages for kernel5Evaluate. Here is the code:

$kern5Path = "C:\\Program Files\\Wolfram Research\\Mathematica\\5.2\\MathKernel.exe";

Clear[printMessage, printPrint, printPostScript]
printMessage[str_String] := 
  CellPrint@
   Cell[BoxData[
     RowBox[StringSplit[str, 
        x : ("MyDelimeterStart" | "MyDelimeterEnd") :> x] //. {x___, 
         "MyDelimeterStart", y_, "MyDelimeterEnd", z___} :> {x, 
         ToExpression[y], z}]], "Message", 
    CellLabel -> "(Kernel 5.2)", ShowCellLabel -> True];
printPostScript = 
  CellPrint@
    Cell[GraphicsData["PostScript", #], "Graphics", 
     CellLabel -> "(Kernel 5.2 PostScript)", ShowCellLabel -> True] &;
printPrint[str_String] := 
  CellPrint@
   Cell[If[StringTake[str, -1] === "\n", StringDrop[str, -1], str], 
    "Print", CellLabel -> "(Kernel 5.2 print, text mode)", 
    ShowCellLabel -> True];

Clear[linkEvaluate]
SetAttributes[linkEvaluate, HoldAllComplete]
linkEvaluate[link_LinkObject, expr_] := Catch[
   Module[{out = {}, postScript = {}, packet, result = Null},
    If[LinkReadyQ[link], 
     While[LinkReadyQ[link], 
      Print["Rest of the buffer:\t", 
       packet = LinkRead[link, Hold]]];
     If[Not@MatchQ[packet, Hold[InputNamePacket[_]]], 
      Message[kernel5Evaluate::linkIsBusy]; Throw[$Failed]]];
    LinkWrite[link, Unevaluated[EnterExpressionPacket[expr]]];
    While[
     Check[Not@
       MatchQ[packet = LinkRead[link, Hold], 
        Hold[InputNamePacket[_]]], 
      Message[kernel5Evaluate::linkIsClosed]; Throw[$Failed]],
     Switch[packet,
      Hold@DisplayPacket[_String], 
      AppendTo[postScript, First@First@packet],
      Hold@DisplayEndPacket[_String], 
      AppendTo[postScript, First@First@packet]; 
      printPostScript@StringJoin[postScript]; postScript = {},
      Hold@MessagePacket[__], ,
      Hold@TextPacket[_String], 
      If[StringMatchQ[First@First@packet, 
        WordCharacter .. ~~ "::" ~~ WordCharacter .. ~~ ": " ~~ __], 
       printMessage[First@First@packet], 
       printPrint[First@First@packet]],
      Hold@OutputNamePacket[_], ,
      Hold@ReturnExpressionPacket[_], result = First[First[packet]],
      _, AppendTo[out, packet]
      ]
     ];
    If[Length[out] > 0, Print["Unparsed packets: ", out]];
    result
    ]];
Clear[kernel5Evaluate]
SetAttributes[kernel5Evaluate, HoldAllComplete]
kernel5Evaluate::usage = "kernel5Evaluate[\!\(\*
StyleBox[\"expr\",\nFontFamily->\"Times New Roman\",\n\
FontSlant->\"Italic\"]\)] writes \!\(\*
StyleBox[\"expr\",\nFontFamily->\"Times New Roman\",\n\
FontSlant->\"Italic\"]\) to MathKernel 5.2, returns output and prints \
messages generated during computation.";
kernel5Evaluate::linkIsBusy = 
  "Kernel 5.2 is still running previous calculation.";
kernel5Evaluate::linkIsClosed = "Connection to Kernel 5.2 is lost.";
kernel5Evaluate::kernel5NotFound = 
  "Path `1` not found. Please set variable $kern5Path to correct path \
to MathKernel 5.2.";
kernel5Evaluate[expr_] :=
 If[TrueQ[MemberQ[Links[], $kern5]],
  If[LinkReadyQ[$kern5]; First[LinkError[$kern5]] == 0, 
   With[{$kern5 = $kern5}, linkEvaluate[$kern5, expr]], 
   LinkClose[$kern5]; kernel5Evaluate[expr]],
  Clear[$kern5];
  If[FileExistsQ[$kern5Path],
   $kern5 = LinkLaunch[$kern5Path <> " -mathlink -noinit"]; 
   LinkRead[$kern5]; LinkWrite[$kern5,
    Unevaluated[
     EnterExpressionPacket[$MessagePrePrint = ("MyDelimeterStart" <> 
          ToString[ToBoxes[#]] <> "MyDelimeterEnd") &; 
      SetOptions[$Output, {PageWidth -> Infinity}];]]]; 
   LinkRead[$kern5]; kernel5Evaluate[expr], 
   Message[kernel5Evaluate::kernel5NotFound, $kern5Path]; $Failed]
  ]

And here are some test expressions:

kernel5Evaluate[Unevaluated[2 + 2]]
kernel5Evaluate[$Version]
kernel5Evaluate[Quit[]]
kernel5Evaluate[Print["some string"];]
kernel5Evaluate[Sin[1,]]
kernel5Evaluate[1/0]

kernel5Evaluate[{Plot[Sin[x], {x, 0, Pi}], 
   Plot[Sin[x], {x, -Pi, Pi}]}] // 
 DeleteCases[#, HoldPattern[DefaultFont :> $DefaultFont], Infinity] &

kernel5Evaluate[Plot3D[Sin[x y], {x, 0, Pi}, {y, 0, Pi}]];
ListPlot3D[First@%, Mesh -> Full, DataRange -> MeshRange /. Last[%]]

s = kernel5Evaluate[
  NDSolve[{y'[x] == y[x] Cos[x + y[x]], y[0] == 1}, y, {x, 0, 30}]]
% // InputForm // Short

kernel5Evaluate[ContourPlot[Sin[x y], {x, -5, 5}, {y, -5, 5}]];
ListContourPlot[First@%, DataRange -> MeshRange /. Last[%], 
 Contours -> 10, 
 Method -> {"Refinement" -> {"CellDecomposition" -> "Quad"}}]

Here's my attempt at what you want,

First I define linkEvaluate that takes an active Link and passes it an expression. If there's things for LinkRead still to read, then it reads them until there are no more. Then it writes the expression and waits for the results to come back. Then it reads the output until there's nothing left to read. Normally, it then returns the first ReturnExpressionPacket unless you have set the final, optional argument, all, to True - in which case it returns everything it read.

Clear[linkEvaluate]
SetAttributes[linkEvaluate, HoldRest]
linkEvaluate[link_LinkObject, expr_, all : (True | False) : False] := 
  Catch[Module[{out = {}},
    While[LinkReadyQ[link], PrintTemporary[LinkRead[link]]];
    If[LinkReadyQ[link], Throw["huh"]];
    LinkWrite[link, Unevaluated[EnterExpressionPacket[expr]]];
    While[! LinkReadyQ[link], Pause[.1]];
    While[LinkReadyQ[link], AppendTo[out, LinkRead[link]]];
    If[all, out, Cases[out, _ReturnExpressionPacket][[1, 1]]]
    ]];

Then kernel5Evaluate first checks if the global $kern5 is defined as a LinkObject, if not then it defines it. It then simply passes the work over to linkEvaluate. You will have to replace "math5" with the filename and path of your Mma 5.2 kernel.

Clear[kernel5Evaluate]
SetAttributes[kernel5Evaluate, HoldAll]
kernel5Evaluate[expr_, all:(True|False):False] := If[TrueQ[MemberQ[Links[], $kern5]], 
  linkEvaluate[$kern5, expr, all], 
  Clear[$kern5]; $kern5 = LinkLaunch["math5 -mathlink"]; kernel5Evaluate[expr,all]
  ]