Re: The uses of Condition (/;)
- To: mathgroup at smc.vnet.net
- Subject: [mg82957] Re: The uses of Condition (/;)
- From: Szabolcs Horvát <szhorvat at gmail.com>
- Date: Mon, 5 Nov 2007 04:56:55 -0500 (EST)
- References: <fghcbl$k9n$1@smc.vnet.net> <fgk9sk$pmk$1@smc.vnet.net>
magma wrote:
> Changing slightly topic:
>
> In the same Condition documentation page we find:
>
> {6, -7, 3, 2, -1, -2} /. x_ /; x < 0 -> w
> giving
> {6, w, 3, 2, w, w}
> and that 's ok. The x_ stand for the individual elements in the list
>
>
> But why then
> {6, -7, 3, 2, -1, -2} /. x_ -> w
> gives
> w
> instead of
> {w,w,w,w,w,w} ?
>
> shouldn't the x_ still stand for the individual elements in the list?
This is because x_ matches the complete list {6, -7, 3, 2, -1, -2}. Try
x_?NumberQ instead or use a level specification:
Replace[{6, -7, 3, 2, -1, -2}, x_ -> w, {1}]
Szabolcs