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.
