what are the possible ways to force mathematica to show -1+a as a-1

I am just getting started with pattern in mathematica. I want to know what the different ways to forc开发者_运维技巧e mma to show -1+a as a-1. Many thanks!

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The simplest way is probably -1 + a // TraditionalForm.

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One due to Jean-Marc Gulliet (MathGroup)

(You may also be interested in the reply of Jens-Peer Kuska to this post)

PolynomialForm[-1 + a, TraditionalOrder -> True]

Out[34]= a-1

(PolynomialForm is undocumented, as far as I know. I am using Mma 7.)

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You could probably use a hack like this

$PrePrint = (# /. -1 + expr__ :> Interpretation[Row[{expr, -1}], expr - 1]) &

But (as WReach suggests) it might be best to use the default Mathematica ordering of expressions and use TraditionalForm when you want it to look more like what a human would write.