Is there a reason why integers are treated so differently to variables?
If, for example, 2 is replaced by a variable, everything works as expected:
h = (k1 + k2)*x
h.subs_expr(k1 + k2 == k3)
k3*x
I don't understand why g is expanded to
2*k1 + 2*k2
but h not to
x*k1 + x*k2
Is there no way to manipulate how an expression is transformed? It would
be a nice feature.
Cheers
Stan
On 25/01/10 20:36, stefan wrote:
Hi Burcin,
thank you, so it won't work what I tried..
Thanks anyway.
STefan
On Monday 25 January 2010 05:41:42 pm Burcin Erocal wrote:
Hi Stefan,
On Mon, 25 Jan 2010 06:49:55 -0800 (PST)
Ichnich<warm...@web.de> wrote:
there seems to be a bug in substitute:
var('k1 k2 k3')
f = (k1+k2)^2
f.substitute(k1+k2==k3)
gives k3^2 as expected.
var('k1 k2 k3')
f = (k1+k2)*2
f.substitute(k1+k2==k3)
gives 2*k1 + 2*k2. The same happens for +2 instead of *2.
In your example, (k1 + k2) is not a subexpression of f, so there is
nothing to substitute.
sage: var('k1 k2 k3')
(k1, k2, k3)
sage: f = (k1+k2)*2
sage: f
2*k1 + 2*k2
sage: f.has(k1+k2)
False
Is there an alternative to do a substitution?
You can rephrase your substitution as k1 == k3 - k2:
sage: f.substitute(k1==k3-k2)
2*k3
Cheers,
Burcin
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