Re: Problem with Position applied on 2D list?

*To*: mathgroup at smc.vnet.net*Subject*: [mg72622] Re: Problem with Position applied on 2D list?*From*: dh <dh at metrohm.ch>*Date*: Fri, 12 Jan 2007 06:13:51 -0500 (EST)*References*: <eo4n23$l4i$1@smc.vnet.net>

Hi Heiko, the problem with your code is that "_" matches everything ( e.g. the head). This works if the match part must contain 5 e.g.the head does not contain 5). But it fails badly otherwise. Therefore, you must be more specific, e.g. instead of "_" the more specific: "{_Integer ..}". Daniel Heiko Damerau wrote: > Dear All, > > There is some strange behaviour of the Position[] function I am > struggling with: > > integerRandomTable = Table[Table[Random[Integer, 10], {10}], {10}]; > > Find the position of all lists containing the value 5 (just a simple > example): > > Position[integerRandomTable, _?(MemberQ[#, 5] &)] > > gives the expected result, e.g. {{1}, {3}, {4}, {5}, {6}, {7}, {8}}. > However, just asking for all lists not containing the value 5 > > Position[integerRandomTable, _?(Not[MemberQ[#, 5]] &)] > > Doesn't give the expected result but some strange thing, e.g. {{0}, > {1,0}, {1, 1}, {1, 2}, {1, 3}, {1, 4}, ..., {10, 3}, {10, 4}, {10, 5}, > {10, 6}, {10, 7}, {10, 8}, {10, 9}, {10, 10}, {10}, {}} > > What is the explanation for the different behaviour of MemberQ[] > and Not[MemberQ[]]? > > Thanks a lot in advance for any help. > > Best regards, > Heiko >