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digitalmars.D.learn - Why 1f.iota(100f).array returns double[] not float[]?

reply drug <drug2004 bk.ru> writes:
import std.array : array;
import std.range : iota;

pragma(msg, typeof(iota(1f, 100f).array)); // why double[] not float[]?

void main()
{
}
Sep 08 2015
parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 09/08/2015 12:00 AM, drug wrote:
 import std.array : array;
 import std.range : iota;

 pragma(msg, typeof(iota(1f, 100f).array)); // why double[] not float[]?

 void main()
 {
 }
It is probably because the type of floating point literals like 1.0 is double. Probably there is a 1.0 in iota's implementation, converting the element type to double according to rule number 2 here: http://dlang.org/type.html#usual-arithmetic-conversions Yep, here it is: https://github.com/D-Programming-Language/phobos/blob/master/std/range/package.d#L4630 auto iota(B, E)(B begin, E end) if (isFloatingPoint!(CommonType!(B, E))) { return iota(begin, end, 1.0); } Although any such expression can become double easily, I think the literal should be 1.0f in this case. Ali
Sep 08 2015
next sibling parent reply "Dominikus Dittes Scherkl" writes:
On Tuesday, 8 September 2015 at 07:17:01 UTC, Ali Çehreli wrote:
 https://github.com/D-Programming-Language/phobos/blob/master/std/range/package.d#L4630

 auto iota(B, E)(B begin, E end)
 if (isFloatingPoint!(CommonType!(B, E)))
 {
     return iota(begin, end, 1.0);
 }
Such kind of stuff would better be written as auto iota(B, E)(B begin, E end) { return iota(begin, end, cast(CommonType!(B, E))1.0); } this doesn't need a constraint anymore, or maybe use if(isNumeric!(CommonType!(B, E))) I tend to use the above kind of cast often, because I like to work with ubyte or ushort, and every f***ing number literal changes the type to uint :-/
Sep 08 2015
parent "Meta" <jared771 gmail.com> writes:
On Tuesday, 8 September 2015 at 12:28:07 UTC, Dominikus Dittes 
Scherkl wrote:
 On Tuesday, 8 September 2015 at 07:17:01 UTC, Ali Çehreli wrote:
 https://github.com/D-Programming-Language/phobos/blob/master/std/range/package.d#L4630

 auto iota(B, E)(B begin, E end)
 if (isFloatingPoint!(CommonType!(B, E)))
 {
     return iota(begin, end, 1.0);
 }
Such kind of stuff would better be written as auto iota(B, E)(B begin, E end) { return iota(begin, end, cast(CommonType!(B, E))1.0); } this doesn't need a constraint anymore, or maybe use if(isNumeric!(CommonType!(B, E))) I tend to use the above kind of cast often, because I like to work with ubyte or ushort, and every f***ing number literal changes the type to uint :-/
Even better, use D's universal construction feature. auto iota(B, E)(B begin, E end) { return iota(begin, end, CommonType!(B, E)(1.0)); }
Sep 08 2015
prev sibling parent reply Steven Schveighoffer <schveiguy yahoo.com> writes:
On 9/8/15 3:17 AM, Ali Çehreli wrote:
 On 09/08/2015 12:00 AM, drug wrote:
 import std.array : array;
 import std.range : iota;

 pragma(msg, typeof(iota(1f, 100f).array)); // why double[] not float[]?

 void main()
 {
 }
It is probably because the type of floating point literals like 1.0 is double. Probably there is a 1.0 in iota's implementation, converting the element type to double according to rule number 2 here: http://dlang.org/type.html#usual-arithmetic-conversions Yep, here it is: https://github.com/D-Programming-Language/phobos/blob/master/std/range/package.d#L4630 auto iota(B, E)(B begin, E end) if (isFloatingPoint!(CommonType!(B, E))) { return iota(begin, end, 1.0); } Although any such expression can become double easily, I think the literal should be 1.0f in this case.
I think this warrants a bug report, iota with only floats as parameters should result in floats. -Steve
Sep 08 2015
parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 09/08/2015 06:37 AM, Steven Schveighoffer wrote:
 I think this warrants a bug report, iota with only floats as parameters
 should result in floats.
https://issues.dlang.org/show_bug.cgi?id=15033 Ali
Sep 08 2015
parent =?UTF-8?B?Ik5vcmRsw7Z3Ig==?= <per.nordlow gmail.com> writes:
On Wednesday, 9 September 2015 at 06:37:17 UTC, Ali Çehreli wrote:
 https://issues.dlang.org/show_bug.cgi?id=15033

 Ali
https://github.com/D-Programming-Language/phobos/pull/3641
Sep 09 2015