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Mathematica: output an expression without evaluating it first

  1. Feb 20, 2013 #1
    Greetings,

    I recently discovered Mathematica's Format function, and it has been of great use to me. However, there is one thing that I want to use it to do, that I have yet to be able to. I could do this easily, though, if there is some Mathematica function that works as follows...

    If I put a semicolon after inputting something in Mathematica, it evaluates what I input without outputting the result. The function that I am looking for is sort of the inverse of this.

    I will call the function DoNotEvaluate[] for the rest of this post. Some simple input and output examples for the function that I am looking for would be...

    Input: DoNotEvaluate[Sqrt[4]]
    Output: Sqrt[4] - note that the output is not 2.

    Input: DoNotEvaluate[Sqrt[2*2]]
    Output: Sqrt[2*2] - note that the output is neither Sqrt[4] or 2.

    Input: x=2*2; DoNotEvaluate[Sqrt[x]]
    Output: Sqrt[4]

    Does anyone know of a Mathematica function, or other Mathematica technique, that does what my made-up DoNotEvaluate[] function does?

    Thanks for any help you can give.

    -HJ Farnsworth
     
  2. jcsd
  3. Feb 20, 2013 #2
    Perhaps one of these or some combination?

    http://reference.wolfram.com/mathematica/ref/HoldForm.html
    http://reference.wolfram.com/mathematica/ref/HoldAll.html
    http://reference.wolfram.com/mathematica/ref/HoldComplete.html
    http://reference.wolfram.com/mathematica/ref/HoldAllComplete.html
    http://reference.wolfram.com/mathematica/ref/Unevaluated.html

    There are even more of these, but I don't think the process of shielding some things from evaluation while getting other things done has been explained in any documentation that I have seen.
     
  4. Feb 20, 2013 #3
    Thank you for the very quick and complete response. That's pretty much what I wanted.

    -HJ Farnsworth
     
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