Jason Merrill wrote:
> On Aug 29, 3:07 am, Burcin Erocal <[EMAIL PROTECTED]> wrote:
>> On Thu, 28 Aug 2008 15:28:03 -0400
>>
>>
>>
>> Tim Lahey <[EMAIL PROTECTED]> wrote:
>>> Hi,
>>> Maple has a really useful feature of inert integrals
>>> and derivatives. Basically, the integrals and derivatives
>>> show up in the equations, but aren't evaluated until
>>> a command to evaluate them is explicitly given. So,
>>> you can delay the evaluation until after you've processed
>>> the expression to the point where it can be evaluated.
>>> This feature comes in very handy during complicated
>>> derivations because you can see which terms are integrals
>>> or derivatives and manipulate them along side
>>> non-integrals/derivatives.
>>> Is there a way to do this in Sage?
>> This is not supported in Sage at the moment, but it is definitely
>> planned. It should be fairly simple to implement this using the new
>> symbolic function interface from ginac, which allows one to specify
>> custom simplify/automatic evaluation functions.
>>
>> I am not familiar with the maple syntax. Can you give some examples of
>> how to use these features so I can play with them without having to dig
>> through documentation?
>
> The Mathematica syntax is Hold[Integral[x,{x,0,1}]]. This remains
> unevaluated until it is wrapped with an Evaluate[]. The nice thing
> about this syntax is that it works for any kind of expression (not
> just integrals).
So maybe we could have something like a FormalExpression class which
does the same thing (has an argument that it doesn't evaluate).
Jason
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