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digitalmars.D.bugs - [Issue 4565] New: In array literals single values can replace arrays of length 1

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=4565

           Summary: In array literals single values can replace arrays of
                    length 1
           Product: D
           Version: D2
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Keywords: accepts-invalid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc


--- Comment #0 from bearophile_hugs eml.cc 2010-08-01 15:27:31 PDT ---
This program compiles with no errors with dmd 2.047:

int[1][3] a1 = [1, 2, 3];
void main() {
    int[1][3] a2 = [1, 2, 3];
}


But those array literals are wrong. This is the correct program:

int[1][3] a1 = [[1], [2], [3]];
void main() {
    int[1][3] a2 = [[1], [2], [3]];
}


A sloppy syntax is bad because it *always* offers space for bugs, like this
one, dmd compiles this program with no errors (note the missing comma):


int[1][3] a = [[1] [0], [2]];
void main() {}


Now a contains [1, 2, 0], a silent bug.
This situation is partially caused by bug 3849

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Aug 01 2010
next sibling parent d-bugmail puremagic.com writes:
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Andrej Mitrovic <andrej.mitrovich gmail.com> changed:

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         AssignedTo|nobody puremagic.com        |andrej.mitrovich gmail.com


--- Comment #1 from Andrej Mitrovic <andrej.mitrovich gmail.com> 2012-10-22
16:00:17 PDT ---
Do you by any chance have a somewhat elaborate set of test-cases that cover
many types of arrays which should and shouldn't compile? It would help to make
solid test-cases.

Otherwise I'll write them myself, no problem.

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--- Comment #2 from bearophile_hugs eml.cc 2012-10-22 16:26:08 PDT ---
(In reply to comment #1)
 Do you by any chance have a somewhat elaborate set of test-cases that cover
 many types of arrays which should and shouldn't compile?
I don't, sorry. Currently finding such test cases is a laborious manual work. There is no fuzzy testing framework for D, as ones used on the certified C compiler. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Oct 22 2012
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yebblies <yebblies gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |pull
                 CC|                            |yebblies gmail.com
           Platform|x86                         |All
         OS/Version|Windows                     |All


--- Comment #3 from yebblies <yebblies gmail.com> 2012-10-28 02:49:25 EST ---
https://github.com/D-Programming-Language/dmd/pull/1207

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--- Comment #4 from Kenji Hara <k.hara.pg gmail.com> 2012-11-15 00:49:19 PST ---
(In reply to comment #0)
 This program compiles with no errors with dmd 2.047:
 
 int[1][3] a1 = [1, 2, 3];
 void main() {
     int[1][3] a2 = [1, 2, 3];
 }

 But those array literals are wrong. This is the correct program:
 
 int[1][3] a1 = [[1], [2], [3]];
 void main() {
     int[1][3] a2 = [[1], [2], [3]];
 }
I think this is not a bad program.
 int[1][3] a1 = [1, 2, 3];
is same as: int[1][3] a1 = void; a1[0][] = 1; // fill all elements by 1 a1[1][] = 2; // fill all elements by 2 a1[2][] = 3; // fill all elements by 3 Then a1 is initialized by [[1], [2], [3]]. And it is consistent with: int[3] sa = 1; // sa is initialized to [1, 1, 1] ----
 A sloppy syntax is bad because it *always* offers space for bugs, like this
 one, dmd compiles this program with no errors (note the missing comma):
 
 int[1][3] a = [[1] [0], [2]];
 void main() {}
[1][0] is an expression which indexing array literal, and evaluated to 1. It's equivalent to: [1,2,3][0] == 1
 Now a contains [1, 2, 0], a silent bug.
Now a is initialized by [1, [2]], and is same as: int[1][3] a = void; a[0][] = 1; a[1] = [2]; a[2][] = 0; // == int.init After all, a == [1, 2, 0]. There is no bug. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Nov 15 2012
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--- Comment #5 from Andrej Mitrovic <andrej.mitrovich gmail.com> 2012-11-15
00:56:56 PST ---
 After all, a == [1, 2, 0]. There is no bug.
Ok, you can close https://github.com/D-Programming-Language/dmd/pull/1207 if bug is invalid. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Nov 15 2012
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--- Comment #6 from bearophile_hugs eml.cc 2013-03-11 19:44:12 PDT ---
(In reply to comment #4)

Sorry for the very delayed answer.

 A sloppy syntax is bad because it *always* offers space for bugs, like this
 one, dmd compiles this program with no errors (note the missing comma):
 
 int[1][3] a = [[1] [0], [2]];
 void main() {}
[1][0] is an expression which indexing array literal, and evaluated to 1. It's equivalent to: [1,2,3][0] == 1
 Now a contains [1, 2, 0], a silent bug.
Now a is initialized by [1, [2]], and is same as: int[1][3] a = void; a[0][] = 1; a[1] = [2]; a[2][] = 0; // == int.init After all, a == [1, 2, 0]. There is no bug.
In my opinion that's probably a bug in user code. I doubt the user meant to write that. Most probably the user meant to write this, but missed a comma after the first sub-array: int[1][3] a = [[1], [0], [2]]; void main() {} But this is an uncommon situation, so I think it's not worth thinking too much about it. What follows is more important:
 I think this is not a bad program.
 int[1][3] a1 = [1, 2, 3];
is same as: int[1][3] a1 = void; a1[0][] = 1; // fill all elements by 1 a1[1][] = 2; // fill all elements by 2 a1[2][] = 3; // fill all elements by 3 Then a1 is initialized by [[1], [2], [3]]. And it is consistent with: int[3] sa = 1; // sa is initialized to [1, 1, 1]
Today this syntax compiles: void main() { int[1][3] a2; a2[0][] = 1; a2[1][] = 2; a2[2][] = 3; } This used to compile fine, but today it gives warnings (and this is good): void main() { int[1][3] a3; a3[0] = 1; a3[1] = 2; a3[2] = 3; } temp.d(3): Warning: explicit element-wise assignment (a3[cast(uint)0])[] = 1 is better than a3[cast(uint)0] = 1 temp.d(4): Warning: explicit element-wise assignment (a3[cast(uint)1])[] = 2 is better than a3[cast(uint)1] = 2 temp.d(5): Warning: explicit element-wise assignment (a3[cast(uint)2])[] = 3 is better than a3[cast(uint)2] = 3 Currently both of the following forms are accepted: void main() { int[1][3] a1 = [[1], [2], [3]]; int[1][3] a2 = [1, 2, 3]; } Generally I trust your good judgement Hara, but if we are going to deprecate the assignment of array slices without using [], then I don't know if the idea of allowing both of those syntaxes is a good idea... -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Mar 11 2013
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Shriramana Sharma <samjnaa gmail.com> changed:

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--- Comment #7 from Shriramana Sharma <samjnaa gmail.com> 2013-05-31 10:33:43
PDT ---
(In reply to comment #4)
 
 I think this is not a bad program.
 int[1][3] a1 = [1, 2, 3];
is same as: int[1][3] a1 = void; a1[0][] = 1; // fill all elements by 1 a1[1][] = 2; // fill all elements by 2 a1[2][] = 3; // fill all elements by 3 Then a1 is initialized by [[1], [2], [3]]. And it is consistent with: int[3] sa = 1; // sa is initialized to [1, 1, 1]
FWIW I agree with bearophile here. In the case of having a single value on the RHS it is easy (?) to construe how int[3] a = 1 (or even maybe int[3][3] a = 1) would initialize all the elements, but when you specify an array literal on the RHS, I think it should have the same shape as the array specified in the type on the LHS to avoid hard-to-find bugs. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
May 31 2013