Hello
(1) -> f:=(y-m)*sqrt(x)/s
+-+
(y - m)\|x
(1) -----------
s
Type:
Expression(Integer)
(2) -> k_sx:= first kernels f
+-+
(2) \|x
Type:
Kernel(Expression(Integer))
(3) -> subst (f,[k_sx],[e*s])
(3) e y - e m
Type:
Expression(Integer)
(4) -> %::POLY INT
(4) e y - e m
Type:
Polynomial(Integer)
(5) -> factor %
(5) e(y - m)
Type:
Factored(Polynomial(Integer))
Regards
Themos Tsikas
On Sunday, 30 September 2018 17:41:57 UTC+1, Slawomir Kolodynski wrote:
> Suppose I have an expression like *(y-m)*sqrt(x)/s* . What I would like
> to do is to give a name *e* to the *sqrt(x)/s* part and do some kind of
> transformation on this expression so that I get *(y-m)*e *or equivalent
> as the result*. *To do that I define a rule
>
> substE := rule (('y-'m)*sqrt('x)/'s == ('y-'m)*'e)
>
> However, when I try to apply this rule to the expression
>
> substE (y-m)*sqrt(x)/s
>
> I get the *(y-m)*sqrt(x)/s *expression back instead of *(y-m)*e. *It
> looks like the left hand side of the equality in the rule substE does not
> pattern match itself.
>
> Curiously, without sqrt a similar rule works as expected:
>
> substF := rule (('y-'m)*'x/'s == ('y-'m)*'e)
>
> substF ((y-m)*x/s)
>
> gives e*y - e*m
>
> Can you explain what is the difference here and how to approach the goal
> of substituting a subexpression with a symbol?
>
> Thanks,
>
> Slawomir
>
>
>
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