Re: replacement x->y except in Exp[x]

*To*: mathgroup at smc.vnet.net*Subject*: [mg110900] Re: replacement x->y except in Exp[x]*From*: Andrzej Kozlowski <akozlowski at gmail.com>*Date*: Sat, 10 Jul 2010 06:33:07 -0400 (EDT)

Actually I is a Symbol, before evaluation: In[90]:= Head[Unevaluated[I]] Out[90]= Symbol but it is no loner one after evaluation: In[91]:= Head[I] Out[91]= Complex Andrzej Kozlowski On 10 Jul 2010, at 17:01, Murray Eisenberg wrote: > I is not a "symbol"! > > Head[I] > Complex > > 3+I /. I-> -I > 3 + I > > Head[2] > Integer > > (2/3) /. 2->5 > 2/3 > > Please stop beating the dead horse. > > > On 7/8/2010 8:34 PM, AES wrote: > >> ...Is it ever a good idea to use ReplaceAll to do word-processing-type >> "global find and replace" changes like this? >> >> Lengthy threads on this NG have pointed out the havoc that this can >> wreak if the symbol I is among those replaced, particularly if one >> attempts to do I -> -I. >> >> Or is I the _only_ symbol in the entire Mathematica vocabulary that >> encounters this difficulty? >> >> (I really would like to know the answer to this question, even if this >> is entirely out of curiosity, not any real need. I've asked it >> previously, and never gotten an answer.) > > > -- > 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 >