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  • C++ inheritance and member function pointers

    - by smh
    In C++, can member function pointers be used to point to derived (or even base) class members? EDIT: Perhaps an example will help. Suppose we have a hierarchy of three classes X, Y, Z in order of inheritance. Y therefore has a base class X and a derived class Z. Now we can define a member function pointer p for class Y. This is written as: void (Y::*p)(); (For simplicity, I'll assume we're only interested in functions with the signature void f() ) This pointer p can now be used to point to member functions of class Y. This question (two questions, really) is then: Can p be used to point to a function in the derived class Z? Can p be used to point to a function in the base class X?

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  • getSymbols and using lapply, Cl, and merge to extract close prices

    - by algotr8der
    I've been messing around with this for some time. I recently started using the quantmod package to perform analytics on stock prices. I have a ticker vector that looks like the following: > tickers [1] "SPY" "DIA" "IWM" "SMH" "OIH" "XLY" "XLP" "XLE" "XLI" "XLB" "XLK" "XLU" "XLV" [14] "QQQ" > str(tickers) chr [1:14] "SPY" "DIA" "IWM" "SMH" "OIH" "XLY" "XLP" "XLE" ... I wrote a function called myX to use in a lapply call to save prices for every stock in the vector tickers. It has the following code: myX <- function(tickers, start, end) { require(quantmod) getSymbols(tickers, from=start, to=end) } I call lapply by itself library(quantmod) lapply(tickers,myX,start="2001-03-01", end="2011-03-11") > lapply(tickers,myX,start="2001-03-01", end="2011-03-11") [[1]] [1] "SPY" [[2]] [1] "DIA" [[3]] [1] "IWM" [[4]] [1] "SMH" [[5]] [1] "OIH" [[6]] [1] "XLY" [[7]] [1] "XLP" [[8]] [1] "XLE" [[9]] [1] "XLI" [[10]] [1] "XLB" [[11]] [1] "XLK" [[12]] [1] "XLU" [[13]] [1] "XLV" [[14]] [1] "QQQ" That works fine. Now I want to merge the Close prices for every stock into an object that looks like # BCSI.Close WBSN.Close NTAP.Close FFIV.Close SU.Close # 2011-01-03 30.50 20.36 57.41 134.33 38.82 # 2011-01-04 30.24 19.82 57.38 132.07 38.03 # 2011-01-05 31.36 19.90 57.87 137.29 38.40 # 2011-01-06 32.04 19.79 57.49 138.07 37.23 # 2011-01-07 31.95 19.77 57.20 138.35 37.30 # 2011-01-10 31.55 19.76 58.22 142.69 37.04 Someone recommended I try something like the following: ClosePrices <- do.call(merge, lapply(tickers, function(x) Cl(get(x)))) However I tried various combinations of this without any success. First I tried just calling lapply with Cl(x) >lapply(tickers,myX,start="2001-03-01", end="2011-03-11") Cl(myX))) > lapply(tickers,myX,start="2001-03-01", end="2011-03-11") Cl(x))) Error: unexpected symbol in "lapply(tickers,myX,start="2001-03-01", end="2011-03-11") Cl" > > lapply(tickers,myX(x),start="2001-03-01", end="2011-03-11") Cl(x))) Error: unexpected symbol in "lapply(tickers,myX(x),start="2001-03-01", end="2011-03-11") Cl" > > lapply(tickers,myX(start="2001-03-01", end="2011-03-11") Cl(x) Error: unexpected symbol in "lapply(tickers,myX(start="2001-03-01", end="2011-03-11") Cl" > lapply(tickers,myX(start="2001-03-01", end="2011-03-11") Cl(x)) Error: unexpected symbol in "lapply(tickers,myX(start="2001-03-01", end="2011-03-11") Cl" > Any guidance would be kindly appreciated.

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  • html doctype adds whitespace ??

    - by pstanton
    can someone please explain to me why having a doctype of <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> and <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"> render the following block differently under firefox? <table style="border-collapse:collapse; margin:0; padding:0;"> <tr> <td style="border:1px solid red; margin:0; padding:0;"><img src="http://images.smh.com.au/2010/06/01/1533814/th_park-90x60.jpg" style="border:none; padding:0; margin:0;" /></td> </tr> </table> using 'Transitional', there is no white space below the image, using 'Strict' there is! 2nd question, using strict, is it at all possible to remove this whitespace?

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