Write x^3 as xxx

Question

I use mathematica compute functions I need for some external coding. However I can't use terms like x^2+y^3 since my programming language needs this term written as x*x+y*y*y. I would love to copy and paste the results from mathematica so how do I convert these terms?

Something like StringReplace["x^2+y^3", a : LetterCharacter ~~ "^" ~~ n : DigitCharacter :> StringRiffle[ConstantArray[a, FromDigits[n]], "*"]]? — J. M.'s missing motivation, Jan 14 '21 at 11:28
Kinda works but kinda not since mathematica dont uses ^ to write a power. — Arji, Jan 14 '21 at 11:29
You can first use ToString@InputForm[expr] to get a string with powers written in ^ notation — Hausdorff, Jan 14 '21 at 11:40
I asked a similar question ten years ago (!!!) about tweaking the output of "CForm" (to change Power to repeated multiplication); Leonid Schifrin wrote a great reply that solved my problem. So it is really quite interesting to me to see the approaches mentioned to this question. — Daniel Chisholm, Jan 14 '21 at 17:37

score 8 · Accepted Answer · answered Jan 14 '21 at 11:47

8

If you want it in string form you can do it like this

x^3 /. Power -> (StringRiffle[#, "*"] &@ConstantArray[#1, #2] &)

"x * x * x"

This makes use of the fact that x^3 is internally written as Power[x,3].

answered Jan 14 '21 at 11:47

AccidentalTaylorExpansion

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1

Works. Thank you! – Arji Jan 14 '21 at 12:00
8

x^3 /. Power[a_, n_] :> Inactive[Times] @@ ConstantArray[a, n] is another way to do it. This makes it easy to convert back as well with Activate. – Sjoerd Smit Jan 14 '21 at 14:41
2

also x^2 + y^3 /. Power -> Apply[Inactive @ Times] @* ConstantArray – kglr Jan 14 '21 at 19:55

score 7 · Answer 2 · answered Jan 14 '21 at 16:26

Since you mention another language, here's a method using CForm:

Unprotect[Power];
Power /: Format[x_Symbol^n_Integer?Positive, CForm] := SequenceForm @@ Riffle[
    ConstantArray[x, n],
    Format["*", OutputForm]
]
Protect[Power];

Example:

x^2+y^3 //CForm
xx + yy*y

Write x^3 as x*x*x

2 Answers2

Write x^3 as xxx