#17958: implement declare_var, deprecate (None)var
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Reporter: rws | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.6
Component: symbolics | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Comment (by nbruin):
Replying to [comment:42 vbraun]:
> Even right row you are not **supposed** to use `var` in library code,
but there is nothing stopping you. Programmatically generated symbolic
variables should always be declared as `x = SR.var('x')`. This is already
spelled out in the current `var` docstring.
Is that spelled out? I looked at sage.calculus.var.var? (that's the var
that also occurs at top-level) and didn't find it there. I don't think a
programmatic approach to injecting `x1,...,x10` is so bad.
A possible scenario:
{{{
sage: A=var(''.join('x%d '%i for i in [1..10]))
sage: L=sum(A[i]^(i+1) for i in [0..9])^2
sage: L.expand().coefficient(x4^4)
2*x10^10 + 2*x9^9 + 2*x8^8 + 2*x7^7 + 2*x6^6 + 2*x5^5 + 2*x3^3 + 2*x2^2 +
2*x1
}}}
which actually illustrates a genuine use of "inject as well as return".
D'oh.
--
Ticket URL: <http://trac.sagemath.org/ticket/17958#comment:46>
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