Thanks, Stavros, for putting up with my density!
I get it now.
However, the documentation on 'solve', 'linsolve', etc., need to be fixed to document this behavior.
I just did '? solve', and the documentation said nothing about this issue.
At 09:52 AM 6/12/2013, Stavros Macrakis wrote:
>Extraneous equations add parameters. As I said, solve gives solutions that are correct for all values of all parameters.
>
>Thus:
>
> solve([x=0],[x]) => [[x=0]]
>
>but
>
> solve([x=0,y=2],[x]) => []
>
>because there is no solution for all values of y, which is considered a parameter, since it is not listed as a variable.
>
>In your example, you have equations like h0 = g0 + f0 - e0 which are composed entirely of parameters.
>
> -s
>
>On Wed, Jun 12, 2013 at 12:21 PM, Henry Baker <hbaker1 at pipeline.com> wrote:
>Your comment doesn't appear to me to be relevant to the particular set of equations that I gave.
>
>The equations are all linear, and solve works fine without the extraneous equations:
>
>(%i22) eqn12;
>(%o22) [d0 = c0 + b0, d1 = c1 + b1, d2 = c2 + b2]
>(%i23) d;
>(%o23) [d0, d1, d2]
>(%i24) solve(eqn12,d);
>(%o24) [[d0 = c0 + b0, d1 = c1 + b1, d2 = c2 + b2]]
>(%i25)
>
>How can the extraneous (linear) equations screw up solve?
>
>At 09:08 AM 6/12/2013, Stavros Macrakis wrote:
>>Solve only gives solutions valid for all values of parameters (as opposed to variables). For example:
>>
>>(%i12) solve([x=a,x=-a],[x]); <<< no solutions for all a
>>(%o12) []
>>(%i13) solve([x=a,x=-a],[x,a]); <<< make a into a variable
>>(%o13) [[x = 0, a = 0]]
>>
>>On Wed, Jun 12, 2013 at 11:38 AM, Henry Baker <hbaker1 at pipeline.com> wrote:
>>Solve doesn't work, either!
>>
>>(%i7) d;
>>(%o7) [d0, d1, d2]
>>(%i8) eqns;
>>(%o8) [d0 = c0 + b0, d1 = c1 + b1, d2 = c2 + b2, h0 = g0 + f0 - e0,
>>h1 = g1 + f1 - e1, h2 = g2 + f2 - e2, f0 = e0 + b0, f1 = e1 + b1,
>>f2 = e2 + b2, g0 = e0 + c0, g1 = e1 + c1, g2 = e2 + c2]
>>(%i9) solve(eqns,d);
>>(%o9) []
>>(%i10)