Re: Any uses for SequenceHold ?
- To: mathgroup at smc.vnet.net
- Subject: [mg7522] Re: [mg7501] Any uses for SequenceHold ?
- From: David Withoff <withoff>
- Date: Tue, 10 Jun 1997 23:17:56 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
> Mma 3.0 has a new Attribute called SequenceHold.
> As far as I can tell this Attribute has no useful application.
>
> In what way would things fail to work if these function didn't have this
> Attribute?
>
> How did ealier versions get by without SequenceHold?
>
> Ted Ersek
> ersek_ted%pax1a at mr.nawcad.navy.mil
Here is Version 3.0:
In[2]:= {x, y, z} /. y -> Sequence[y1, y2, y3]
Out[2]= {x, y1, y2, y3, z}
This works because Rule has the SequenceHold attribute.i
In Version 2.2 this generates an error message and fails.
Dave Withoff
Wolfram Research