Re: list mutability (very basic question)
- To: mathgroup at smc.vnet.net
- Subject: [mg131716] Re: list mutability (very basic question)
- From: Alan G Isaac <alan.isaac at gmail.com>
- Date: Mon, 23 Sep 2013 21:58:30 -0400 (EDT)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
- Delivered-to: l-mathgroup@wolfram.com
- Delivered-to: mathgroup-outx@smc.vnet.net
- Delivered-to: mathgroup-newsendx@smc.vnet.net
- References: <20130921083830.751226A65@smc.vnet.net> <201309220228.36832.itais@wolfram.com>
On 9/22/2013 3:28 AM, Itai Seggev wrote:> Do you think that 0=1 should not be an error? If
> you think it should be an error (as it is in every language I'm familiar with),
> then why should {0}[[1]]=1, which would essentially be the same thing, not be
> an error?
Because I do not expect this syntax to lead to the LHS to be evaluated to 0.
I expect it to mean: replace the first element of the list {0} with the value 1.
(Compare Python: ``[0][0]=1`` is not an error, for exactly this reason.)
In fact this is a key point of puzzlement for me:
why ``x={0};x[[1]]=1`` is ok but ``{0}[[1]]=1`` is an error in Mathematica.
What is the evaluation rule for the LHS that produces this difference?
Thanks,
Alan
- References:
- list mutability (very basic question)
- From: Alan <alan.isaac@gmail.com>
- list mutability (very basic question)