Re: delayed rule evaluation order
- To: mathgroup at smc.vnet.net
- Subject: [mg67999] Re: [mg67967] delayed rule evaluation order
- From: "Chris Chiasson" <chris at chiasson.name>
- Date: Thu, 20 Jul 2006 06:04:41 -0400 (EDT)
- References: <11710934.1153306359682.JavaMail.root@eastrmwml07.mgt.cox.net>
- Sender: owner-wri-mathgroup at wolfram.com
Thanks to Kozlowski's, Hanlon's and Pein's solutions (haven't received
any others so far), I am now using this type of replacement:
Hold[5.55555555]/.{blah_?InexactNumberQ:>
junk[SetPrecision[blah,3]]}/.junk->Evaluate
Hold[5.56]
However, this still does not totally work on Trace's output:
In[1]:=
f[1]=1;
f[n_Integer]/;n>1=n f[n-1];
InputForm[z=Trace[f[2]]]
Out[3]//InputForm=
{HoldForm[f[2]], {HoldForm[2 > 1], HoldForm[True]}, HoldForm[2*f[-1 + 2]],
{{HoldForm[-1 + 2], HoldForm[1]}, HoldForm[f[1]], HoldForm[1]},
HoldForm[2*1], HoldForm[2]}
In[4]:=
InputForm[z/.{blah_?ExactNumberQ:>junk[SetPrecision[blah,3]]}/.junk->Evaluate]
Out[4]//InputForm=
{HoldForm[2.`2.9999999999999996], {HoldForm[Evaluate[SetPrecision[2,
3]] > Evaluate[SetPrecision[1, 3]]],
HoldForm[True]}, HoldForm[2.`2.9999999999999996],
{{HoldForm[1.`2.9999999999999996], HoldForm[1.`2.9999999999999996]},
HoldForm[1.`2.9999999999999996],
HoldForm[1.`2.9999999999999996]}, HoldForm[2.`2.9999999999999996],
HoldForm[2.`2.9999999999999996]}
Notice the leftover Evaluate and SetPrecision commands. Does anyone
have ideas on how to get this to work?
On 7/19/06, Bob Hanlon <hanlonr at cox.net> wrote:
> Hold[{2, 3}] /.
> {Hold[{x_, y_}] :> Hold[Evaluate[x^y]]}
>
> Hold[8]
>
>
> Bob Hanlon
>
> ---- Chris Chiasson <chris at chiasson.name> wrote:
> > Hold[{2, 3}] /. {{x_, y_} :> x^y}
> >
> > the result is Hold[Power[2,3]]
> >
> > I would like the result to be Hold[8]
> >
> > The original context is post-processing of a large Trace output (via
> > SetPrecision to get rid of digits and improve readability).
> >
> > Any ideas?
> >
> > --
> > http://chris.chiasson.name/
> >
>
> --
>
> Bob Hanlon
> hanlonr at cox.net
>
>
>
--
http://chris.chiasson.name/