Re: Bug in Sum causes index variable to remain set?

*To*: mathgroup at smc.vnet.net*Subject*: [mg33868] Re: [mg33838] Bug in Sum causes index variable to remain set?*From*: "Martin Jenkins" <lamarth at optushome.com.au>*Date*: Sat, 20 Apr 2002 02:50:10 -0400 (EDT)*References*: <200204190628.CAA13520@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

I'm sorry, it appears that all lines starting with "F r o m" have been deleted from my original message. So much for copy as text+paste from Mathematica. It should have looked more like this: Hello, I have found what appears to be a bug in Sum in Mathematica 4.0. I stumbled across is trying to sum an expression with subscripts. Anyway: In[1]:= n = 1; In[2]:= Sum[1, {f[x, 1], 1, 3}] Out[2]= 3 In[3]:= ?f fr In[3]:= "Global`f" In[4]:= Sum[1, {f[x, n], 1, 3}] Out[4]= 3 In[5]:= ?f fr In[5]:= "Global`f" fr In[5]:= f[x, 1] = 3 In[6]:= Clear[f]; In[7]:= Sum[1, {f[x, 1*1], 1, 3}] Out[7]= 3 In[8]:= ?f fr In[8]:= "Global`f" fr In[8]:= f[x, 1] = 3 The way that f gets set by the Sum to the final value is a bug is it not? I would guess that Sum unsets the literal expression f[x, n] or f[x, 1*1], rather than exactly what it set in the first place. I can get around this by f[x,n]=. whenever I use it... but I would rather not have a line with a comment saying "Mathematica bug work-around". Integrate works fine under similar circumstances. Thanks, Martin

**References**:**Bug in Sum causes index variable to remain set?***From:*"Martin Jenkins" <lamarth@optushome.com.au>