Re: Evaluate[expr]
- To: mathgroup at smc.vnet.net
- Subject: [mg123509] Re: Evaluate[expr]
- From: "Oleksandr Rasputinov" <oleksandr_rasputinov at hmamail.com>
- Date: Fri, 9 Dec 2011 05:57:29 -0500 (EST)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
- References: <201112071114.GAA04233@smc.vnet.net> <jbq3pv$ip9$1@smc.vnet.net>
f[x_] = x^5 - 3 x^2 + 1;
tt = Table[{{x}, f[x], Evaluate@D[f[x], x]}, {x, 0, 2, 0.3}]
does not work. This is because Evaluate exists only to override Hold*
attributes when it appears directly as an argument to a function that has
such attributes. In the above case where Evaluate appears nested inside a
List, this is a null operation (as List has no Hold* attributes to
override) and Evaluate is not seen by Table.
On Thu, 08 Dec 2011 10:33:35 -0000, Murray Eisenberg
<murray at math.umass.edu> wrote:
> The Evaluate expression -- here could be wrapped just around the part
> D[f[x],x]] -- once and for all evaluates the symbolic derivative.
>
> On 12/7/11 6:14 AM, =E9=81=93 =E5=8E=9A wrote:
>> f[x_] = x^5 - 3 x^2 + 1; tt =
>> Table[Evaluate[{{x}, f[x], D[f[x], x]}], {x, 0, 2, 0.3}]
>>
>> In the above expression , what's the function of Evaluate[expr]?
>>
>> Why doesn't it work without Evaluate[expr]?
>>
>> Can you help me?
>>
>
> --
> Murray Eisenberg murray at math.umass.edu
> Mathematics & Statistics Dept.
> Lederle Graduate Research Tower phone 413 549-1020 (H)
> University of Massachusetts 413 545-2859 (W)
> 710 North Pleasant Street fax 413 545-1801
> Amherst, MA 01003-9305
- References:
- Evaluate[expr]
- From: é å <shlwell1988@gmail.com>
- Evaluate[expr]