Re: broadcasting of Equal ? (newbie question)
- To: mathgroup at smc.vnet.net
- Subject: [mg118185] Re: broadcasting of Equal ? (newbie question)
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Sat, 16 Apr 2011 07:31:50 -0400 (EDT)
This is covered in the documentation for Thread
Thread[f[{a, b, c}, x]]
{f[a, x], f[b, x], f[c, x]}
Let f be Equal
Thread[Equal[{a, b, c}, x]]
{a == x, b == x, c == x}
which is the same as
Thread[{a, b, c} == x]
{a == x, b == x, c == x}
Your question just uses a shorter list.
Bob Hanlon
---- Alan <alan.isaac at gmail.com> wrote:
=============
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