code D'ish enough? - ignore previous post with same subject
Jordan Wilson via Digitalmars-d-learn
digitalmars-d-learn at puremagic.com
Sun Feb 26 13:50:38 PST 2017
On Sunday, 26 February 2017 at 19:34:33 UTC, thorstein wrote:
> Hi,
>
> sorry for posting again, but I used a keyboard combination that
> accidently send my post before it was done.
>
> Coming more or less from Python I just started with D. Not a
> real programmer, just automating things and looking for a neat
> compiled language.
>
> Just to learn, I wrote a function to read CSV-like files (I
> know D has its own routine). Since I'm still a bit overwhelmed
> by the many complex language features, I'm curious what could I
> change to make my code as D'ish as possible?
>
> Thank you for any suggestion,
> Thorstein
>
> // Reads CSV-like files with only numeric values in each column
> // new_ndv replaces ndv, which is the original no-data-value
> double[][]* readNumMatCsv(char[] filePath, int numHeaderLines,
> char[] ndv, char[] new_ndv)
> { double[][]* p_numArray;
> double[][] numArray;
> char[] line;
> string noCont = "File content not usable. Quit here.";
> string noFile = "Could not read file. Quit here.";
> string nonNum = "Found a non-numeric value in data matrix.
> Quit here.";
> Regex!char re = regex(r"(\n$)");
>
> if(exists(filePath))
> { File f = File(filePath, "r");
> if((line = f.readln().dup).length > 0)
> { while (!f.eof())
> // 1st replace ndv with new_ndv, 2nd remove all \n, 3rd
> check id size of read line >0
> { if((line = replaceAll(f.readln().dup.replace(ndv,
> new_ndv), re, "")).length > 0)
> // check if all elements of splitted line are numeric
> { foreach(i;split(line,","))
> { if(isNumeric(i) == false)
> // otherwise return pointer to empty array
> { writeln(nonNum);
> return p_numArray;
> }
> }
> // convert characters to double
> if(split(line,",").length > 0)
> { numArray ~= to!(double[])(split(line,","));
> }
> }
> }
> // pass reference to pointer
> p_numArray = &numArray;
> // first line empty -> return pointer to empty array
> } else { writeln(noCont); }
> // file could not be find
> } else { writeln(noFile); }
> return p_numArray;
> }
I'm in a similar boat, as I continue to learn D, I find myself
using UFCS, "auto", and operating on ranges alot more; I think
that's considered idiomatic.
For example, here is my rough attempt:
auto readNumMatCsv2 (string filePath, string ndv, string new_ndv){
double[][] p_numArray;
try {
auto lines = File(filePath,"r").byLine;
lines.popFront; // get read of header
p_numArray = lines.map!(a => a.replace (ndv,new_ndv)
.splitter (",")
.map!(a => a.to!double)
.array)
.array;
} catch (Exception e){
e.msg.writeln; // this replaces "Could not read file.
Quit here."
}
return p_numArray;
}
It took me quite a while to get the whole usage of range stuff
like "map" and "filter" etc., but I think it's worth the effort.
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