http://d.puremagic.com/issues/show_bug.cgi?id=2101

           Summary: Please may I use mutable arrays at compile time?
           Product: D
           Version: 2.013
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla@digitalmars.com
        ReportedBy: caron800@googlemail.com


The docs say I can't use non-const arrays at compile-time. But I want to, so this is an enhancement request.

The following does not compile.

    int ctfeTest()
    {
        char[10] a; // <--- PROBLEM
        return 1;
    }

    const int A = ctfeTest();

This does

    int ctfeTest()
    {
        char[] a; // <--- OK
        return 1;
    }

but that's completely pointless. This doesn't:

    int ctfeTest()
    {
        char[] a = new char[10]; // <--- PROBLEM
        return 1;
    }

Nor does this:

    int ctfeTest()
    {
        char[] a;
        a.length = 10; // <--- PROBLEM
        return 1;
    }

Even if we can't have dynamic arrays, what's the harm with static ones?


-- 

http://d.puremagic.com/issues/show_bug.cgi?id=2101





------- Comment #1 from samukha@voliacable.com  2008-05-12 11:41 -------
You could use something like this (quickly hacked, dmd 1.029):

T[] newCtfeArray(T)(size_t size)
{
    T[] array;
    if (!size)
        return array;

    array ~= T.init;

    if (array.length < size)
        return newCtfeArray(array, size);

    return array;
}

private T[] newCtfeArray(T, U = void)(T[] array, size_t size)
{
    while (array.length * 2 <= size)
        array ~= array;

    if (array.length < size)
        return array ~= newCtfeArray!(T)(size - array.length);

    return array;
}

int[] test()
{
    // Allocate an array of 123 ints. The memory will not be freed, sigh
    auto a = newCtfeArray!(int)(123);
    foreach (i, e; a)
    {
        a[i] = e;
    }

    return a;
}

void main()
{
    static const a = test();
}


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http://d.puremagic.com/issues/show_bug.cgi?id=2101


Don <clugdbug@yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch


--- Comment #3 from Don <clugdbug@yahoo.com.au> 2010-01-10 14:11:14 PST ---
Janice's first case has compiled for quite a long time now. The third case, involving 'new', is very straightforward.  The final case (changing length) is doubtful whether it is a good idea. I think with implementing 'new', we can close this bug.

PATCH to allow dynamic array creation with new. Insert this code into interpret.c, around line 2690. Also add the declaration for it in NewExp in expression.h. Also need to change the spec to remove the restriction on using 'new'.

------------
Expression *NewExp::interpret(InterState *istate)
{
#if LOG
    printf("NewExp::interpret() %s\n", toChars());
#endif
    if (newtype->ty == Tarray && arguments && arguments->dim == 1)
    {
    Expression *lenExpr = ((Expression
*)(arguments->data[0]))->interpret(istate);
    if (lenExpr == EXP_CANT_INTERPRET)
        return EXP_CANT_INTERPRET;
    return createBlockDuplicatedArrayLiteral(newtype,
        newtype->defaultInitLiteral(), lenExpr->toInteger());
    }
    error("Cannot interpret %s at compile time", toChars());
    return EXP_CANT_INTERPRET;
}

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bugzilla@digitalmars.com


--- Comment #4 from Walter Bright <bugzilla@digitalmars.com> 2010-01-11 22:58:37 PST ---
Changeset 333.

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


--- Comment #5 from Walter Bright <bugzilla@digitalmars.com> 2010-01-30 22:40:30 PST ---
fixed dmd 1.056 and 2.040

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