# How to avoid applying Cross to a single argument?

I am looking for the simplest way to avoid applying Cross to a single argument.

PrimeFactorization[x_] := Cross @@ (Superscript @@@ FactorInteger[x]);
Table[{n, PrimeFactorization[n]}, {n, 200, 250}] // TableForm


• What about If? – Kuba Aug 16 '18 at 8:00
• Down vote detected. Thank you! – Friendly Ghost Aug 17 '18 at 12:55

Since you already use Cross in a way that it's not meant to be used, you can also redefine it and assign a meaning to it when it has only a single argument:

Unprotect[Cross];
Cross[x_] := x;


A bit less severe: Define your own function.

cross[x__] := Cross[x];
cross[x_] := x;


If it is only for displaying purposes you can use Row:

PrimeFactorization[x_] := Row[#, "\[Cross]"] & @ (Superscript @@@ FactorInteger[x])

• This solution is not TeXForm friendly. Thank you! – Friendly Ghost Aug 16 '18 at 8:10
• @FriendlyGhost there is nothing about TeXForm in your question. – Kuba Aug 16 '18 at 8:12
• @FriendlyGhost, use BoxForm$UseTemplateSlotSequenceForRow = False; before using TeXForm on expressions involving Row.(See Incompatibility of Row and TeXForm) – kglr Aug 17 '18 at 8:12 You might define your own function cross, that calls Cross when the number of arguments is larger than 1: cross=If[Length[{##}]>1, Cross[##], #]&;  • Thanks. Is there any method to check the number of arguments instead of using your trick with Length[{...}]? – Friendly Ghost Aug 16 '18 at 8:03 An alternative solution without defining new functions: PrimeFactorization[x_] := Superscript @@@ FactorInteger[x] /. y_ /; Length@y < 0 -> Cross @@ y  For displaying purposes you can also use: Times @@ Defer@*Power @@@ FactorInteger[10!] CenterDot @@ Superscript @@@ FactorInteger[10!] Inactive[Times] @@ Superscript @@@ FactorInteger[10!]  • (+1) This does not resolve the issue with numbers that are a power if a prime though. – Henrik Schumacher Aug 16 '18 at 16:59 You can use Block in two ways: 1. temporarily re-define Cross so that Cross[t_] := t: PrimeFactorization[x_] := Block[{Cross}, Cross[t_] := t; Cross @@ Superscript @@@ FactorInteger @ x]; PrimeFactorization /@ {211, 222, 223} // TeXForm $\left\{211^1,2^1\times 3^1\times 37^1,223^1\right\}$1. temporarily define Sequence as Cross: PrimeFactorization2[x_] := Block[{Sequence = Cross}, ## & @@ Superscript @@@ FactorInteger @ x]; PrimeFactorization2 /@ {211, 222, 223} // TeXForm `$\left\{211^1,2^1\times 3^1\times 37^1,223^1\right\}\$