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Re: How to work with In?
*To*: mathgroup at smc.vnet.net
*Subject*: [mg113996] Re: How to work with In?
*From*: kj <no.email at please.post>
*Date*: Sat, 20 Nov 2010 06:12:49 -0500 (EST)
*References*: <ic5opg$70l$1@smc.vnet.net>
In <ic5opg$70l$1 at smc.vnet.net> Oliver Ruebenkoenig <ruebenko at wolfram.com> writes:
>On Fri, 19 Nov 2010, kj wrote:
>> I want to create a list consisting of the (unevaluated) expressions
>> that were entered in a particular subrange of the In array. I.e.,
>> what I want is (almost) something like this:
>>
>> Table[In[i], {i, 300, 375}]
>>
>> except that this won't work, because each In[i] will be evaluated.
>> This also fails
>>
>> Table[Hold[In[i]], {i, 300, 375}]
>>
>> because now the i is not evaluated, so the result is a list of
>> multiple copies of the expression Hold[In[i]].
>>
>> How can I do what I'm trying to do?
>I think this is your friend
>Table[With[{i = i}, Hold[In[i]]], {i, 300, 375}]
That's one cool trick! Thanks!
Unfortunately, it doesn't solve this problem:
In[31]:= Table[With[{i = i}, Hold[In[i]]], {i, 20, 30}]
Out[31]= {Hold[In[20]], Hold[In[21]], Hold[In[22]], Hold[In[23]],
Hold[In[24]], Hold[In[25]], Hold[In[26]], Hold[In[27]], Hold[In[28]],
Hold[In[29]], Hold[In[30]]}
I need each of In[20], In[21], ..., In[30] to be processed by the
kernel exactly once before clamping the result with Hold.
By the way, being able to limit the level of evaluation to a precise
number of "passes", greater than zero, but not all the way to full
evaluation, is something I find myself needing very often.
~kj
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