Re: delayed rule evaluation order
- To: mathgroup at smc.vnet.net
- Subject: [mg68009] Re: [mg67967] delayed rule evaluation order
- From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
- Date: Thu, 20 Jul 2006 06:04:50 -0400 (EDT)
- References: <11710934.1153306359682.JavaMail.root@eastrmwml07.mgt.cox.net> <acbec1a40607190514x62d0f07byeb91cf8b496bca33@mail.gmail.com> <3BA57237-C0B6-4C71-A8B0-3481DCDBC464@mimuw.edu.pl> <acbec1a40607190919p3efa8b30x4ae0cb6278444931@mail.gmail.com> <330E5DE6-73D2-4844-BACD-8D96B736EA76@mimuw.edu.pl> <F2BDC55B-557A-4968-B933-18548988AD0B@mimuw.edu.pl>
- Sender: owner-wri-mathgroup at wolfram.com
O maybe that is not so ideal after all, since f got evaluated. You
can of course combine it with the Block technique I used earlier.
Andrzej
On 19 Jul 2006, at 19:03, Andrzej Kozlowski wrote:
> Here is another way, which you may like better. It uses the blah
> approach and the Trott-Strzebonski partial evaluation technique.
>
> f[1] = 1;
> f[n_Integer] /; n > 1 = n f[n - 1];
> InputForm[z = Trace[f[2]]];
>
> v = z /. {blah_?ExactNumberQ :> SetPrecision[blah, 3]};
>
>
>
> v/.p_SetPrecision:> With[{eval = p}, eval /; True]
>
>
> {2.00,{2.00>1.00,True},2.00,{{1.00,1.00},1.00,1.00},2.00,2.00}
>
> This must be finally what you wanted, isn't it?
>
> Andrzej Kozlowski
>
>
>
> On 19 Jul 2006, at 18:50, Andrzej Kozlowski wrote:
>
>> It's much easier to answer questions if the persons who pose them
>> explain clearly what they mean.
>>
>> The most obvious way to modify my code seems to me to be:
>>
>>
>> f[1] = 1;
>> f[n_Integer] /; n > 1 = n f[n - 1];
>> InputForm[z = Trace[f[2]]];
>>
>>
>> Block[{f=g},z/.{HoldForm[a_]:>HoldForm@@{SetPrecision[a,3]}}]/.g->f
>>
>>
>> {f(2.00),{True,True},2.00 f(1.00),{{1.00,1.00},f(1.00),1.00},
>> 2.00,2.00}
>>
>> Now f is not evaluated. The only thing you might still complain
>> about is that {2 > 1, True} evaluated to {True,True}. If you
>> really care about this you, can prevent it in various ways, for
>> example:
>>
>>
>> Block[{f=g},
>> z/.{HoldForm[a_]/;
>> FreeQ[a,True]:>HoldForm@@{SetPrecision[a,3]}}]/.g->f
>>
>>
>> {f(2.00),{2>1,True},2.00 f(1.00),{{1.00,1.00},f(1.00),1.00},
>> 2.00,2.00}
>>
>> or
>>
>>
>> Block[{f=g,Greater=greater},
>> z/.{HoldForm[a_]/;
>> FreeQ[a,True]:>HoldForm@@{SetPrecision[a,3]}}]/.{g-
>> >f,greater->Greater}
>>
>>
>> {f(2.00),{2.00>1.00,True},2.00 f(1.00),{{1.00,1.00},f(1.00),1.00},
>> 2.00,2.00}
>>
>>
>> There are many other possibilities.
>> If there is still anything you do not like than it probably means
>> you still have not explained completely what you want.
>>
>> Andrzej Kozlowski
>>
>> On 19 Jul 2006, at 18:19, Chris Chiasson wrote:
>>
>>>
>>> What I want it to do is be able to replace numbers that aren't
>>> direct
>>> arguments of HoldForm (maybe they are nested a few levels deep,
>>> etc).
>>>
>>> In the example you sent me, f is evaluated - which is undesirable
>>> for me.
>>>
>>> On 7/19/06, Andrzej Kozlowski <akoz at mimuw.edu.pl> wrote:
>>>> (tm) Pro*
>>>> It seems to me that a variant of my first suggestion works fine:
>>>>
>>>> In[1]:=
>>>> f[1]=1;
>>>> f[n_Integer]/;n>1=n f[n-1];
>>>> InputForm[z=Trace[f[2]]];
>>>> InputForm[z/.{HoldForm[a_]:>HoldForm@@{SetPrecision[a,3]}}]
>>>>
>>>> Out[4]//InputForm=
>>>> {HoldForm[2.`2.9999999999999973],
>>>> {HoldForm[True], HoldForm[True]},
>>>> HoldForm[2.`2.9999999999999973],
>>>> {{HoldForm[1.`2.9999999999999973],
>>>> HoldForm[1.`2.9999999999999973]},
>>>> HoldForm[1.`2.9999999999999973],
>>>> HoldForm[1.`2.9999999999999973]},
>>>> HoldForm[2.`2.9999999999999973],
>>>> HoldForm[2.`2.9999999999999973]}
>>>>
>>>> Or is this not what you wanted?
>>>>
>>>> Andrzej Kozlowski
>>>>
>>>>
>>>>
>>>> On 19 Jul 2006, at 14:14, Chris Chiasson wrote:
>>>>
>>>> > 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/
>>>>
>>>>
>>>
>>>
>>> --
>>> http://chris.chiasson.name/
>>
>