wolfram-mathematica,wolfram-language

Use Quiet to suppress the warning messages, then select number cases. Slist = FinancialData["NASDAQ:*", "Lookup"]; Dlist = Cases[Quiet[{#, FinancialData[#]} & /@ Slist], {_, _?NumberQ}] ...

wolfram-mathematica,wolframalpha,wolfram-language

After the usual lots of trial and error that WolframAlpha didn't understand, finally WolframAlpha PrimeOmegaPlot link...

c++,bison,flex-lexer,wolfram-language

yylex is defined in the generated scanner and used (automatically) in the generated parser. Since the results are just ordinary C(++), there is no magic; if you use yylex in a file, you need to declare it in that file. You might expect bison to include the declaration automatically, but...

wolfram-mathematica,wolfram-language

Switch may be useful, for example: Switch[ # , _String , StringLength[#] , _List , Length[#] , __ , Null ] & /@ { "abc", {1, 2, 3, 4}, Pi} {3, 4, Null} ...