Re: Integrate[ ] returns If[ ] function; how to say it's True?
- To: mathgroup at smc.vnet.net
- Subject: [mg9395] Re: [mg9359] Integrate[ ] returns If[ ] function; how to say it's True?
- From: Allan Hayes <hay at haystack.demon.co.uk>
- Date: Sun, 2 Nov 1997 01:02:25 -0500
- Sender: owner-wri-mathgroup at wolfram.com
Sat, 1 Nov 1997 03:33:46 -0500 siegman at ee.stanford.edu (AES) T[mg9359] Integrate[ ] returns If[ ] function; how to say it's True? > Doing an Integrate[ ] returns an If[condition,a,b] result, with > complicated expressions for condition, a, and b. > I want to get B as input for the next cell (automatically, not by > just copying it by hand). > How can I get at the "parts" of the If[ ] statement, or use it in a > subsequent Input[ ] cell with condition set equal to True? Let's take In[1]:= int =Integrate[x^n,{x,0,1}] Out[1]= 1 n If[Re[n] > -1, -----, Integrate[x , {x, 0, 1}]] 1 + n We can easily get the 1/(1+n) In[2]:= int[[2]] Out[2]= 1 ----- 1 + n But int[[3]] immediately evaluates to Out[1], so we may want to hold it: In[3]:= Extract[int,3, Hold] Out[3]= n Hold[Integrate[x , {x, 0, 1}]] Other holding functions might be used, for example Unevaluated. Allan Hayes hay at haystack.demon.co.uk http://www.haystack.demon.co.uk/training.html voice:+44 (0)116 2714198 fax: +44 (0)116 2718642 Leicester, UK