Re: how many times nestwhile repeats calculations?

*To*: mathgroup at smc.vnet.net*Subject*: [mg71970] Re: [mg71944] how many times nestwhile repeats calculations?*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>*Date*: Wed, 6 Dec 2006 06:04:03 -0500 (EST)*References*: <200612051104.GAA27219@smc.vnet.net>

On 5 Dec 2006, at 20:04, Arkadiusz.Majka at gmail.com wrote: > Hi, > >> From Help Browser we read > > NestWhile[f, expr, test] starts with expr, then repeatedly applies f > until applying test to the result no longer yields True. > > I would like to know how many times f is applied till test stops > everything. I read already a post in which the following example was > presented > > In[1]:= mysqrt[a_] := NestWhile[{#[[1]]+1, .5(#[[2]]+a/#[[2]])}&, > {0, Max[1.,N@a]}, #[[2]]^2 > a&] > In[2]:= mysqrt[2] > Out[2]= {5, 1.41421} > > > Do you know any other method? I don't want to influence to NestWhile > (by inserting a "counting" element #[[1]]+1 ) > > Thanks, > > Arek > mysqrt[a_] := With[{v = NestWhileList[0.5*(#1 + a/#1) & , Max[1., N[a]], #1^2 > a & ]}, {Length[v] - 1, Last[v]}] mysqrt[2] {5, 1.414213562373095} Andrzej Kozlowski

**References**:**how many times nestwhile repeats calculations?***From:*Arkadiusz.Majka@gmail.com