Re: Difficulty with patterns

• To: mathgroup at smc.vnet.net
• Subject: [mg122305] Re: Difficulty with patterns
• From: Armand Tamzarian <mike.honeychurch at gmail.com>
• Date: Mon, 24 Oct 2011 05:14:37 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <j80qbl\$ae1\$1@smc.vnet.net>

```On Oct 23, 9:30 pm, "McHale, Paul" <Paul.McH... at excelitas.com> wrote:
> I have recently become increasingly uncomfortable with my areas of ignorance with Mathematica.  The Virtual conference has some really cool demos.  In one, a website is read in and a table of data extracted.  Without patterns, it would have been very difficult.  Need a little help with an example.
>
> Example 1 uses my old standby, the Table[] function.  Works fine.  I am attempting to get better with patterns, so I tried example 2 and 3.  They work, but gives several errors about use of stringjoin needing strings.  What am I doing wrong?
>
> Error: StringJoin::string: String expected at position 1 in StringJoin[n].
>
> (* Load string from WolframAlpha  *)
> m WolframAlpha["usa",{{"LargestCities:CountryData",1},"ComputableData"},
> PodStates->{"LargestCities:CountryData__More","LargestCities:CountryData__More"}];
>
> (* example 1 *)
> mNew=Flatten[m,1];
> mNew=Drop[mNew,1];
> mNew=Drop[mNew,-1];
> mNew=Table[{i[[1,1]] <> i[[1,2]] <> i[[1,2]] ,i[[2]]},{i,mNew}];
> Grid[mNew,Frame->All]
>
> (* example 2 *)
> Clear[n,o,p,q];
> mNew=Cases[m, {{n_String,o_String,p_String},q_} -> { n <>  ", " <> o <> ", " <>  p,q},Infinity ];
> Grid[mNew,Frame->All]
>
> (* example 3 *)
> Clear[n,o,p,q];
> mNew=Cases[m, {{n_,o_,p_},q_} -> { n ,  ", ", o  , ", ", p,q},Infinity ];
> mNew = mNew /. {n___,q_Integer} -> {StringJoin[n],q};
> Grid[mNew,Frame->All]
>
> I even tried,
> mNew = Flatten[m, 1];
> mNew = Drop[mNew, 1];
> mNew = Drop[mNew, -1];
>     i[[2]]}, {i, mNew}];
> (*mNew=Table[{i[[1,1]] <> i[[1,2]] <> i[[1,2]] ,i[[2]]},{i,mNew}];*)
> Grid[mNew, Frame -> All]
>
> They are all strings!
>
> Thanks,
> Paul
>
> Paul McHale  |  Electrical Engineer, Energetics Systems  |  Excelitas Technologies Corp.
> =09
> Phone:   +1 937.865.3004   |   Fax:  +1 937.865.5170   |   Mobile:   +1 937.371.2828
> 1100 Vanguard Blvd, Miamisburg, Ohio 45342-0312 USA
> Paul.McH... at Excelitas.comwww.excelitas.com
>
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it is a bit subtle. You need to use RuleDelayed for this operation