Re: expressions list -> equations list

*To*: mathgroup at smc.vnet.net*Subject*: [mg83979] Re: expressions list -> equations list*From*: Szabolcs Horvát <szhorvat at gmail.com>*Date*: Thu, 6 Dec 2007 02:39:34 -0500 (EST)*References*: <fj6404$em9$1@smc.vnet.net>

Hauke Reddmann wrote: > 1st of all THX to all who answered my last question. Just one other before > I lend a Mathematica manual from the public lib and pester you no more :-) > > So. Now that I have a tensor it must vanish identically. I Flatten[] it first > and then I have a list of equations...oh, stop, I haven't. REDUCE (if I may > mention the name of a competition :-) could take a Solve[] now because it > automatically assumes a "=0" as default but Mathematica is anally-retentive > (a good thing :-) and I somehow must turn {a,b,c} into {a=0,b=0,c=0}. > Convert to string, global change "," -> "=0," and "}" -> "=0}", reconvert > to list? Is that possible? Or is there a less LISP-hack-style solution? > Note that in Mathematica a = 0 is an assignment. If you need to assign values to several undefined symbols, then {a, b, c} = {0, 0, 0} will work. If you need to build a list of equations then try # == 0 & /@ {a, b, c} or Thread[{a,b,c} == 0] both of which yield {a==0, b==0, c==0} But Solve[] seems to accept vector-equations too: In[1]:= Solve[{a, b, c} == 0, {a, b, c}] Out[1]= {{a -> 0, b -> 0, c -> 0}} In[2]:= Solve[{a, b, c} == {1, 2, 3}, {a, b, c}] Out[2]= {{a -> 1, b -> 2, c -> 3}} If it doesn't work for some reason, then use Thread[]: In[3]:= Thread[{a, b, c} == {1, 2, 3}] Out[3]= {a == 1, b == 2, c == 3} -- Szabolcs