patterns question

Questions
1

Hello everyone, I’m newbie.
Why in {1, x^1, x^2, x^3} /. x^n_ → r[n] out {1, x, r[2], r[3]} ?
I expected {1, r[1], r[2], r[3]}

Thanks in advance.

2

Hi,

That is since x^1 is automatically evaluated to x. Compare:

x^1 // FullForm
x^n // FullForm

Use HoldForm[] to get what you expect:

HoldForm[{1, x^1, x^2, x^3}] /. x^n_ -> r[n]

I.M.