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Re: broadcasting of Equal ? (newbie question)

  • To: mathgroup at smc.vnet.net
  • Subject: [mg118175] Re: broadcasting of Equal ? (newbie question)
  • From: Alan <alan.isaac at gmail.com>
  • Date: Fri, 15 Apr 2011 03:57:04 -0400 (EDT)
  • References: <io6d27$dq9$1@smc.vnet.net>

One response I received off list suggested that I should not even
Solve with the first form, but rather should Thread it first:
Thread[{x + y - 1, 2 x + y - 2} == {0, 0}]. In fact, I was doing this
until I found I did not need to to get a correct response from Mathematica.

That just adds to my question: the forms I showed work.  Is that an
accident, or does it reflect a reliable rule?  Can you point me to the
the rule(s)?

Btw, Thread appears to allow the same kind of "broadcasting" behavior,
and again I could not anticipate that from the documentation I found.

In[7]:= Thread[{x + y - 1, 2 x + y - 2} == 0]

Out[7]= {-1 + x + y == 0, -2 + 2 x + y == 0}

So again, is this an accidental success, or a reliable rule? And if a
rule, what is it and where documented?

Thanks,
Alan Isaac


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