digitalmars.D - initialization immutable array
- AntonSotov (57/57) May 15 2014 DMD 2.065
- Yota (27/41) May 15 2014 You're only allowed to assign an immutable value in a constructor
- Steven Schveighoffer (9/64) May 15 2014 Assign _items only once in the constructor.
- AntonSotov (13/45) May 15 2014 thanks for example!
- Steven Schveighoffer (5/17) May 15 2014 I didn't speak clearly, I understand that it currently "works", but that...
- =?UTF-8?B?QWxpIMOHZWhyZWxp?= (4/5) May 15 2014 Done:
- Jacob Carlborg (8/21) May 15 2014 This might not bet what you were asking for, but alternativly you could
- monarch_dodra (2/5) May 16 2014 UFCS iota :puke:
- bearophile (5/6) May 16 2014 I think UFCS iota is acceptable when it has only one argument:
- monarch_dodra (9/15) May 16 2014 My gripe is how "incompatible" 1-arg and 2-arg iota is w.r.t.
- bearophile (8/12) May 16 2014 Yes, I understand.
- Jacob Carlborg (5/6) May 16 2014 Yeah, it would make more sense if it would be called "upto":
DMD 2.065
I do not know much English. sorry.
need to initialize immutable array "_items"
//-------------------------------------------------------
module main;
import std.stdio;
class Zond {
this() {
foreach (i; 1..4) {
_items ~= i; // is expected ERROR
}
}
immutable(int[]) _items;
}
int main(string[] args)
{
// create
auto zond = new Zond();
// test output
foreach (it; zond._items) {
writeln(it);
}
return 0;
}
//-------------------------------------------------------
this method does not work:
Error: field _items initializing not allowed in loops or after
labels.
OK! is expected - I read in a book Alexandrescu.
Make a small change, I add a nested function "addItem":
//-------------------------------------------------------
module main;
import std.stdio;
class Zond {
this() {
void addItem(in int value) {
_items ~= value; // OK , why?
}
foreach (i; 1..4) {
addItem(i);
}
}
immutable(int[]) _items;
}
int main(string[] args)
{
// create
auto zond = new Zond();
// test output
foreach (it; zond._items) {
writeln(it);
}
return 0;
}
//-------------------------------------------------------
This method initialization works. why?
I do not understand the difference.
May 15 2014
"Yota" <yotaxp thatGoogleMailThing.com>
On Thursday, 15 May 2014 at 16:13:59 UTC, AntonSotov wrote:
DMD 2.065
I do not know much English. sorry.
need to initialize immutable array "_items"
//-------------------------------------------------------
module main;
import std.stdio;
class Zond {
this() {
foreach (i; 1..4) {
_items ~= i; // is expected ERROR
}
}
immutable(int[]) _items;
}
You're only allowed to assign an immutable value in a constructor
once, which is why it doesn't let you do so in a loop. As for
the second example, that looks like a bug to me.
Here are a couple ways to initialize the array:
1:
this() {
import std.exception : assumeUnique;
int[] items;
foreach (i; 1..4) {
items ~= i;
}
_items = items.assumeUnique;
}
2:
this() {
// The result of a pure function may be implicitly cast to
immutable.
_items = function() pure {
int[] items;
foreach (i; 1..4) {
items ~= i;
}
return items;
}();
}
BTW, this would be better suited to the digitalmars.D.learn group.
May 15 2014
On Thu, 15 May 2014 12:13:58 -0400, AntonSotov <nepuvive rainmail.biz> wrote:DMD 2.065 I do not know much English. sorry. need to initialize immutable array "_items" //------------------------------------------------------- module main; import std.stdio; class Zond { this() { foreach (i; 1..4) { _items ~= i; // is expected ERROR } } immutable(int[]) _items; } int main(string[] args) { // create auto zond = new Zond(); // test output foreach (it; zond._items) { writeln(it); } return 0; } //------------------------------------------------------- this method does not work: Error: field _items initializing not allowed in loops or after labels.Assign _items only once in the constructor. immutable(int)[] tmp; foreach(i; 1..4) tmp ~= i; _items = tmp;Make a small change, I add a nested function "addItem": //------------------------------------------------------- module main; import std.stdio; class Zond { this() { void addItem(in int value) { _items ~= value; // OK , why? } foreach (i; 1..4) { addItem(i); } } immutable(int[]) _items; } int main(string[] args) { // create auto zond = new Zond(); // test output foreach (it; zond._items) { writeln(it); } return 0; } //------------------------------------------------------- This method initialization works. why? I do not understand the difference.This should not work IMO. -Steve
May 15 2014
On Thursday, 15 May 2014 at 17:15:50 UTC, Steven Schveighoffer wrote:Assign _items only once in the constructor. immutable(int)[] tmp; foreach(i; 1..4) tmp ~= i; _items = tmp;thanks for example! On Thursday, 15 May 2014 at 17:15:50 UTC, Steven Schveighoffer wrote:This should not work IMO.My second example compiles successfully and displays the correct result - that's why I became interested in why it works. you can compile yourself. On Thursday, 15 May 2014 at 16:58:04 UTC, Yota wrote:Here are a couple ways to initialize the array: 1: this() { import std.exception : assumeUnique; int[] items; foreach (i; 1..4) { items ~= i; } _items = items.assumeUnique; } 2: this() { // The result of a pure function may be implicitly cast to immutable. _items = function() pure { int[] items; foreach (i; 1..4) { items ~= i; } return items; }(); }thanks for example! On Thursday, 15 May 2014 at 16:58:04 UTC, Yota wrote:As for the second example, that looks like a bug to me.if this is actually a bug - will be good if someone could register it.
May 15 2014
On Thu, 15 May 2014 14:18:03 -0400, AntonSotov <nepuvive rainmail.biz> wrote:On Thursday, 15 May 2014 at 17:15:50 UTC, Steven Schveighoffer wrote:I didn't speak clearly, I understand that it currently "works", but that is a bug. It shouldn't work. -SteveAssign _items only once in the constructor. immutable(int)[] tmp; foreach(i; 1..4) tmp ~= i; _items = tmp;thanks for example! On Thursday, 15 May 2014 at 17:15:50 UTC, Steven Schveighoffer wrote:This should not work IMO.My second example compiles successfully and displays the correct result - that's why I became interested in why it works. you can compile yourself.
May 15 2014
On 05/15/2014 11:18 AM, AntonSotov wrote:if this is actually a bug - will be good if someone could register it.Done: https://issues.dlang.org/show_bug.cgi?id=12749 Ali
May 15 2014
On 15/05/14 18:13, AntonSotov wrote:
DMD 2.065
I do not know much English. sorry.
need to initialize immutable array "_items"
//-------------------------------------------------------
module main;
import std.stdio;
class Zond {
this() {
foreach (i; 1..4) {
_items ~= i; // is expected ERROR
}
}
immutable(int[]) _items;
This might not bet what you were asking for, but alternativly you could
use "iota":
import std.algorithm;
import std.range;
immutable(int[]) _items = 1.iota(4).array;
--
/Jacob Carlborg
May 15 2014
On Friday, 16 May 2014 at 06:37:30 UTC, Jacob Carlborg wrote:import std.algorithm; import std.range; immutable(int[]) _items = 1.iota(4).array;UFCS iota :puke:
May 16 2014
monarch_dodra:UFCS iota :puke:I think UFCS iota is acceptable when it has only one argument: myArray.length.iota... Bye, bearophile
May 16 2014
On Friday, 16 May 2014 at 08:43:31 UTC, bearophile wrote:monarch_dodra:My gripe is how "incompatible" 1-arg and 2-arg iota is w.r.t. UFCS: 0.iota(4); 4.iota(); That's also why I've stopped using "writeln()" as UFCS: It "looks" convenient at first, but then you want to turn those "writeln" into "writefln", and that's when things don't go according to plan...UFCS iota :puke:I think UFCS iota is acceptable when it has only one argument: myArray.length.iota... Bye, bearophile
May 16 2014
monarch_dodra:That's also why I've stopped using "writeln()" as UFCS: It "looks" convenient at first, but then you want to turn those "writeln" into "writefln", and that's when things don't go according to plan...Yes, I understand. If you want some ugly code you can use std.functional.binaryReverseArgs: alias flip = binaryReverseArgs; myRange.flip!writefln("%s") bye, bearophile
May 16 2014
On 16/05/14 10:32, monarch_dodra wrote:UFCS iota :puke:Yeah, it would make more sense if it would be called "upto": 1.upto(4) -- /Jacob Carlborg
May 16 2014