In order to use the UnitStep of Mathematica 5.2, I have to install two different versions 5.2 and 11.3 at the same time because Unitstep is different in the two versions (UnitStep has different derivatives in the two different verions of Mathematica, I listed the difference here). Today I suddenly think of that: Can I call the old version UnitStep of MMA 5.2 in the new Mathematica 11.3? How to realize if it's true? Thank you.

  • $\begingroup$ @ Nasser, the MathKernel.exe will not run, but the math.exe can run in the CMD window correctly. $\endgroup$
    – likehust
    Commented Nov 8, 2019 at 2:22
  • 2
    $\begingroup$ You can use version 5.2 Kernel from newer kernel via MathLink: "Executing code in v.5.2 kernel from within v.7.01 session through MathLink." $\endgroup$ Commented Nov 8, 2019 at 6:52
  • $\begingroup$ @AlexeyPopkov, thank you, it's a good solution, but too complex and easily generates error. I continue to combine 5.2 and 11.3 because I can debug codes with ease. $\endgroup$
    – likehust
    Commented Nov 8, 2019 at 7:49
  • $\begingroup$ I'm curious, what you mean by "I continue to combine 5.2 and 11.3"? How do you do that? $\endgroup$ Commented Nov 8, 2019 at 8:05
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    $\begingroup$ @AlexeyPopkov, To use 5.2 when deriving symbolic formulas because it always gives anticipating results using UnitStep, then use 11.3 when calculating and plotting because the graphics are better in 11.3 than in 5.2 $\endgroup$
    – likehust
    Commented Nov 8, 2019 at 8:08


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