Re: problem with Pick

*To*: mathgroup at smc.vnet.net*Subject*: [mg78234] Re: [mg78194] problem with Pick*From*: "Chris Chiasson" <chris at chiasson.name>*Date*: Tue, 26 Jun 2007 04:36:56 -0400 (EDT)*References*: <acbec1a40706230431p4f1db9a9i4320680dda027396@mail.gmail.com>

I agree 100% with your assessment of what is probably happening, but I also note that this is in violation of Pick's documentation. I also think Pick's present behavior in this situation neither is nor should be intended. On 6/25/07, Andrzej Kozlowski <akoz at mimuw.edu.pl> wrote: > *This message was transferred with a trial version of CommuniGate(tm) Pro* > > On 25 Jun 2007, at 20:06, Chris Chiasson wrote: > > > Step to reproduce: > > 1. Evaluate these two inputs with a fresh kernel: > > Pick[{a,b},z[{},{1}],{__}] > > In[78]:= Pick[{a, b}, {{}, {1}}, {__Integer}] > > Out[78]= {b} > > > > Expected results: > > {b} > > {b} > > > > Actual results: > > {b} > > {a,b} > > > > Relevant Documentation: > > Pick[list,sel,patt] picks out those list[[i1,i2,...]] for which > > sel[[i1,i2,...]] matches patt. > > > > Relevant Evaluation: > > In[3]:= MatchQ[{},{__}] > > Out[3]= False > > > > In[4]:= {Internal`$CreationID,$Version} > > Out[4]= {853857,6.0 for Microsoft Windows (32-bit) (April 27, 2007)} > > > > -- > > http://chris.chiasson.name/ > > > > > But of course > > MatchQ[{{}, {1}}, {__}] > True > > In other words, there is a Match at the top level in exactly the same > way as here: > > Pick[{a, b}, {}, {___}] > {a, b} > > > You can avoid the top level match, by using, for example, > > Pick[{a, b}, {{}, {1}}, {__Integer}] > {b} > > Andrzej Kozlowski > -- http://chris.chiasson.name/