Question: isolating terms using 'select'

Hi:

i am trying to pick off some terms programatically from a list of expressions/equations, and am having some trouble.

consider:


> select(has, y+3*x(t), x); # works
                                                                                                 3 x(t)
> select(has, x(t), x); # not what i would expect - I want x(t)
                                                                                                   x()
> select(has, x(t), y); # even more weird!.. i would expect 0 here.
                                                                                                   x()

My guess is that somehow in the last two cases, x(t) is not treated as an expression. If that's the case, how do i force maple to treat it as such?

thanks!

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