Re: ReplaceList and //.
- To: mathgroup at smc.vnet.net
- Subject: [mg73597] Re: ReplaceList and //.
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Fri, 23 Feb 2007 04:22:26 -0500 (EST)
- Organization: Uni Leipzig
- References: <erjo1u$nn5$1@smc.vnet.net>
- Reply-to: kuska at informatik.uni-leipzig.de
Hi,
and what say the online help ??
?ReplaceAll
expr /. rules applies a rule or list
of rules in an attempt to transform each
subpart of an expression expr.
?ReplaceRepeated
expr //. rules repeatedly performs replacements until expr no longer
changes.
Regards
Jens
Mr Ajit Sen wrote:
> Dear Mathgroup,
>
> Could someone please enlighten me as to when I should
> use ReplaceList and when to use //. in pattern
> matching.
>
> Thus, if Y = a x^2/b^3, then
>
> ReplaceList[Y, a^m_. x^n_. b^p_. :> z
> b^(p + 1) a^(m - 1) x^(n - 1)][[1]]
>
> as well as
>
> Y //. a^m_. x^n_. b^p_. :> z b^(p + 1) a^(m - 1)
> x^(n - 1)
>
> give the same result.
>
> However,
>
> ReplaceList[a*b*c, {(x_)*(y_) -> x^y, (x_)*(y_)
> -> x + y}]
>
> and
> a*b*c //. {(x_)*(y_) :> x^y, (x_y)*_ :> x + y}
>
> yield different outputs.
>
> What am I missing here?
>
> Thanks in advance.
>
>
> Ajit Sen.
>
>
>
>
>
>
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