• Saurabh Das (14/14) Jan 11 2016 I am trying to create 2 types which contain integral values but
• Tobi G. (5/8) Jan 11 2016 You can do something like this:
• Saurabh Das (20/29) Jan 11 2016 Oh excellent. Yes that works for a standalone conversion. Do you
• Tobi G. (14/15) Jan 11 2016 Yes. Because Typedef is introducing new Types, which csvReader
• Saurabh Das (6/22) Jan 11 2016 Yes that does make sense. I could read in a POD struct and

Saurabh Das <saurabh.das gmail.com> writes:

I am trying to create 2 types which contain integral values but 
should not be compatible with each other. std.typecons.Typedef 
seems perfect for this:

alias QuestionId = Typedef!(long, long.init, "QuestionId");
alias StudentId = Typedef!(long, long.init, "StudentId");

However I'm failing to use using std.conv.to:
QuestionId q = to!QuestionId("34"); <-- gives compile errors

(This is a reduced example, the actual use case is to use std.csv 
to read in a structure from file, which in turn calls to!xyz)

How can I get std.conv to understand std.typecons.Typedef? In 
general, is there a better solution to orthogonal types than 
Typedef?

Thanks,
Saurabh

Tobi G. <gruen_tobias web.de> writes:

On Monday, 11 January 2016 at 08:03:19 UTC, Saurabh Das wrote:
 How can I get std.conv to understand std.typecons.Typedef?

You can do something like this:

QuestionId q = to!(TypedefType!QuestionId)("43");

 In general, is there a better solution to orthogonal types than 
 Typedef?

Typedef is a reasonably solution, for this in my opinion.

togrue

Saurabh Das <saurabh.das gmail.com> writes:

On Monday, 11 January 2016 at 12:01:30 UTC, Tobi G. wrote:
 On Monday, 11 January 2016 at 08:03:19 UTC, Saurabh Das wrote:
 How can I get std.conv to understand std.typecons.Typedef?

 You can do something like this:

 QuestionId q = to!(TypedefType!QuestionId)("43");

 In general, is there a better solution to orthogonal types 
 than Typedef?

 Typedef is a reasonably solution, for this in my opinion.

 togrue

Oh excellent. Yes that works for a standalone conversion.  Do you 
know how I can use this with std.csv?

import std.typecons;
alias QuestionId = Typedef!(long, long.init, "QuestionId");
alias StudentId = Typedef!(long, long.init, "StudentId");

struct MyStuff
{
     QuestionId q;
     StudentId s;
}

void main()
{
     import std.csv, std.stdio, std.algorithm, std.range;
     
File("file.csv").byLine.joiner("\n").csvReader!(MyStuff)(null).array;
}

This doesn't work. But if MyStuff is defined as: struct MyStuff { 
int q, s; }, then it works.

Any ideas?

Tobi G. <gruen_tobias web.de> writes:

On Monday, 11 January 2016 at 12:15:55 UTC, Saurabh Das wrote:
 Any ideas?

Yes. Because Typedef is introducing new Types, which csvReader 
doesn't know what they are,
you'll need a little workaround and cast the values yourself.

import std.csv, std.stdio, std.algorithm, std.range;

enum csvTxt = "10, 20
30, 40
50, 50";

myStuff = csvTxt.csvReader!(Tuple!(long, long))
	.map!(a => MyStuff(cast(QuestionId)a[0], cast(StudentId) a[1]))
         .array;


The .map does nothing other as getting the information out of the 
Tuple 'a' and constructing a struct of the type MyStuff.

togrue

Saurabh Das <saurabh.das gmail.com> writes:

On Monday, 11 January 2016 at 12:59:05 UTC, Tobi G. wrote:
 On Monday, 11 January 2016 at 12:15:55 UTC, Saurabh Das wrote:
 Any ideas?

 Yes. Because Typedef is introducing new Types, which csvReader 
 doesn't know what they are,
 you'll need a little workaround and cast the values yourself.

 import std.csv, std.stdio, std.algorithm, std.range;

 enum csvTxt = "10, 20
 30, 40
 50, 50";

 myStuff = csvTxt.csvReader!(Tuple!(long, long))
 	.map!(a => MyStuff(cast(QuestionId)a[0], cast(StudentId) a[1]))
         .array;


 The .map does nothing other as getting the information out of 
 the Tuple 'a' and constructing a struct of the type MyStuff.

 togrue

Yes that does make sense. I could read in a POD struct and 
convert it to a typed one.

Though I was hoping for a more elegant solution... This'll have 
to do I guess.

Thanks!