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

Question

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", "\<\............
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.

Answer 1

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...