Re: Mapping with partial
(it's not on line 79 obviously, you got me :D)
Re: Mapping with partial
On Monday, 30 March 2015 at 18:23:32 UTC, Adam D. Ruppe wrote: On Monday, 30 March 2015 at 18:07:18 UTC, matovitch wrote: kmeans_example.d(79): Error: template std.algorithm.iteration.map That error is easy: use points[].map!(test) instead of points.map. Since points is a static array, it isn't a range. Static arrays can't be popped through. But if you slice it, then it yields a usable range for map. The other problem though is the partial!(). It expects a template argument for the thing so it can make a new function right there at compile time... which doesn't work with a runtime variable. The way I'd do it is just with a little hand written delegate. This will compile, for example: auto test = (ref Point p) = getRandomPoint(randVar, p); points[].map!(test); and should do what you need. Nice ! Thanks for the tip ! I tried importing std.range and points.array works too.
Re: Mapping with partial
Well I have a bit of a similar problem with foreach. If I use classic T[] range, I can do : foreach(int i, auto t, myRange)... But if I use an Array!T (from std.container) I get : cannot infer argument types, expected 1 argument, not 2 Even if I add the brackets []. Any idea ? Thanks for your help ! :)
Re: Mapping with partial
On Monday, 30 March 2015 at 18:29:32 UTC, matovitch wrote: I tried importing std.range and points.array works too. Aye, that would work too, but the slice I think is more efficient as I'm pretty sure... not completely sure, but I think .array makes a copy of static arrays, whereas the slice doesn't.
Re: Mapping with partial
On Monday, 30 March 2015 at 19:11:10 UTC, matovitch wrote: That settle the point for array as for [] ? I though that was clear. [] doesn't copy. I guess the documentation should have something to say about it too. ;) hopefully
Re: Mapping with partial
On Monday, 30 March 2015 at 19:08:24 UTC, anonymous wrote:
On Monday, 30 March 2015 at 18:37:53 UTC, matovitch wrote:
On Monday, 30 March 2015 at 18:34:19 UTC, Adam D. Ruppe wrote:
[...]
Aye, that would work too, but the slice I think is more
efficient as I'm pretty sure... not completely sure, but I
think .array makes a copy of static arrays, whereas the slice
doesn't.
I was going to ask you the question does it just add the range
shell or does it make a copy ? :/ Maybe someone else know.
Let's check the documentation.
http://dlang.org/phobos/std_array.html#array says: Allocates
an array and initializes it with copies of the elements of
range r. Documentation says copy.
Let's check the actual behaviour.
void main()
{
int[1] a = [1];
import std.array: array;
a.array[0] = 2;
import std.stdio: writeln;
writeln(a[0]);
}
(also at http://dpaste.dzfl.pl/1191144a9acf)
This program prints 1. That's the output we'd expect when
`array` makes a copy. Actual behaviour says copy.
So, copy.
That settle the point for array as for [] ? I guess the
documentation should have something to say about it too. ;)
Re: Mapping with partial
On Monday, 30 March 2015 at 19:15:25 UTC, matovitch wrote: Language ref - Array - Slice An array slice does not copy the data, it is only another reference to it. So the total slice of a static array is a range using the underlying memory of the static array isnt it ? yes
Re: Mapping with partial
On Monday, 30 March 2015 at 19:31:54 UTC, anonymous wrote:
On Monday, 30 March 2015 at 19:03:05 UTC, matovitch wrote:
Well I have a bit of a similar problem with foreach.
If I use classic T[] range, I can do :
foreach(int i, auto t, myRange)...
But if I use an Array!T (from std.container) I get :
cannot infer argument types, expected 1 argument, not 2
Even if I add the brackets []. Any idea ? Thanks for your help
! :)
The index is the problem. Generally, foreach doesn't do
automatic indices for ranges. You can use std.range.enumerate
or count yourself explicitly.
foreach(i, t; myRange.enumerate) {...}
size_t i = 0;
foreach(t; myRange) {... ++i;}
Is it a compiler problem or a language restriction ? Thanks for
the workaround btw, I will try it !
Re: Mapping with partial
Language ref - Array - Slice An array slice does not copy the data, it is only another reference to it. So the total slice of a static array is a range using the underlying memory of the static array isnt it ?
Re: Mapping with partial
On Monday, 30 March 2015 at 19:03:05 UTC, matovitch wrote:
Well I have a bit of a similar problem with foreach.
If I use classic T[] range, I can do :
foreach(int i, auto t, myRange)...
But if I use an Array!T (from std.container) I get :
cannot infer argument types, expected 1 argument, not 2
Even if I add the brackets []. Any idea ? Thanks for your help
! :)
The index is the problem. Generally, foreach doesn't do automatic
indices for ranges. You can use std.range.enumerate or count
yourself explicitly.
foreach(i, t; myRange.enumerate) {...}
size_t i = 0;
foreach(t; myRange) {... ++i;}
Re: Mapping with partial
On Monday, 30 March 2015 at 18:34:19 UTC, Adam D. Ruppe wrote: On Monday, 30 March 2015 at 18:29:32 UTC, matovitch wrote: I tried importing std.range and points.array works too. Aye, that would work too, but the slice I think is more efficient as I'm pretty sure... not completely sure, but I think .array makes a copy of static arrays, whereas the slice doesn't. I was going to ask you the question does it just add the range shell or does it make a copy ? :/ Maybe someone else know.
Re: Mapping with partial
Thanks. On a sader note, I found a respons'less thread about my second question : http://forum.dlang.org/thread/mailman.2247.1353945423.5162.digitalmars-d-le...@puremagic.com where std.container.Array is concerned: how come I can't use a foreach(i, x; myArray) formulation? I.e. one where the foreach can infer the index value as well as the contained value ...
Re: Mapping with partial
On Monday, 30 March 2015 at 18:37:53 UTC, matovitch wrote:
On Monday, 30 March 2015 at 18:34:19 UTC, Adam D. Ruppe wrote:
[...]
Aye, that would work too, but the slice I think is more
efficient as I'm pretty sure... not completely sure, but I
think .array makes a copy of static arrays, whereas the slice
doesn't.
I was going to ask you the question does it just add the range
shell or does it make a copy ? :/ Maybe someone else know.
Let's check the documentation.
http://dlang.org/phobos/std_array.html#array says: Allocates an
array and initializes it with copies of the elements of range r.
Documentation says copy.
Let's check the actual behaviour.
void main()
{
int[1] a = [1];
import std.array: array;
a.array[0] = 2;
import std.stdio: writeln;
writeln(a[0]);
}
(also at http://dpaste.dzfl.pl/1191144a9acf)
This program prints 1. That's the output we'd expect when
`array` makes a copy. Actual behaviour says copy.
So, copy.
Re: Mapping with partial
On Monday, 30 March 2015 at 18:07:18 UTC, matovitch wrote: kmeans_example.d(79): Error: template std.algorithm.iteration.map That error is easy: use points[].map!(test) instead of points.map. Since points is a static array, it isn't a range. Static arrays can't be popped through. But if you slice it, then it yields a usable range for map. The other problem though is the partial!(). It expects a template argument for the thing so it can make a new function right there at compile time... which doesn't work with a runtime variable. The way I'd do it is just with a little hand written delegate. This will compile, for example: auto test = (ref Point p) = getRandomPoint(randVar, p); points[].map!(test); and should do what you need.
Re: Mapping with partial
On Mon, 30 Mar 2015 19:36:49 +, matovitch wrote:
The index is the problem. Generally, foreach doesn't do automatic
indices for ranges. You can use std.range.enumerate or count yourself
explicitly.
foreach(i, t; myRange.enumerate) {...}
size_t i = 0;
foreach(t; myRange) {... ++i;}
Is it a compiler problem or a language restriction ?
it is by design. `foreach` is not a fancy for with hidden counter, it's
more high-level construct. so if range isn't providing the counter,
`foreach` will not guess why, and simply doesn't provide it too.
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