On Mar 4, 10:59 am, Jason Grout <[EMAIL PROTECTED]> wrote:
> This morning I tried to copy a matrix output, edit it, and create a new
> matrix. It was frustrating because there seemed to be no way to easily
> cut and paste output into input. This afternoon a person I was showing
> Sage to also had the same concern.
I like the idea of a _sage_init_ method, but implementing it could be
a lot of work depending on the exact specification.
Jason presumably wants output that's easy to read (since he wants to
edit it and paste it back in). William (from IRC last night) wants
output that can be evaluated with sage_eval to get the original value
back.
These goals are difficult to reconcile; the big problem is that
sage_eval only takes a single expression. This means that _sage_init_
on a polynomial must return things like:
"GF(17)['x,y']('3*x^2*y^3')"
or
"GF(17)(3)*GF(17)['x,y'].gen(0)^2*GF(17)['x,y'].gen(1)^3"
or
"(lambda R: (lambda x,y: 3*x^2*y^3)(*R.gens()))(GF(17)['x,y'])"
none of which are very nice.
Options I see include:
1) Give up on having the output work in the initial environment (as
used by sage_eval); instead, assume that generators (polynomial
variables, etc.) are available in the environment.
2) Modify sage_eval so that it can process a sequence of statements
followed by an expression; then _sage_init_ could return
"""
R1 = GF(17)
R2 = R1['x,y']
x, y = R2.gens()
3*x^2*y^3
"""
3) Live with ugly output like the above examples, with lots of
repeated work, or ugly nested lambdas, or ugly nested strings.
Another question is whether floating-point numbers should read back to
the exact same value, or whether it's OK to lose the bottom few bits
(my vote is for "exact same value", of course).
My vote is for option 2), modify sage_eval and have _sage_init_
potentially produce a sequence of statements followed by an
expression; and I'd be interested in helping to implement that option.
Carl
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