Re: Templates, D way

[Computermatronic via Digitalmars-d]

On Tuesday, 5 September 2017 at 12:54:20 UTC, Void-995 wrote:
On Tuesday, 5 September 2017 at 12:20:14 UTC, crimaniak wrote:
On Tuesday, 5 September 2017 at 11:08:57 UTC, Void-995 wrote:
	@property mixin(DataList!("firstSublist", 
MyBinarySubStructAForA, firstSublistMembersCount, 
firstSublistMembersOffset));
 I don't think string mixins are required here. It seems just 
template is more simple.

T[] getBytesAs(T, alias length, alias offset)()
{
    return (cast(T *)(cast(byte *)(&this) + offset))[0 .. 
length];
}

struct MyBinaryStructA
{
 ...
    alias firstList = getBytesAs!(MyBinarySubStructAForA, 
firstSublistMembersCount, firstSublistMembersOffset);
    alias secondList = getBytesAs!(MyBinarySubStructBForA, 
secondSublistMembersCount, secondSublistMembersOffset);
}

unittest
{
...
    MyBinaryStructA *binaryData = cast(MyBinaryStructA 
*)fileData.ptr;

    auto a = binaryData.firstList;
}

Thanks, that definitely working and doesn't require mixin with 
strings. But while waiting for response I've tried another 
thing, and I doubt I would able do to that without string now:

template MyBinaryStructGenericDataList(string listName, alias 
Type)
{
        import std.string;

        const char[] MyBinaryStructGenericDataList = format(q{
                int %sCount;
                int %sOffset;

                @property %s[] %s() const
                {
			return (cast(%s *)(cast(ubyte *)(&this) + %sOffset))[0 .. 
%sCount];
                }
	}, listName, listName, Type.stringof, listName, Type.stringof, 
listName, listName);
}

struct MyBinarySubStructAForA
{
        int someIntegerFieldA;
        float someFloatFieldA;
}

struct MyBinarySubStructBForA
{
        int someIntegerFieldB;
        float someFloatFieldB;
}

struct MyBinaryStructA
{
	mixin(MyBinaryStructGenericDataList!("firstSublist", 
MyBinarySubStructAForA));
	mixin(MyBinaryStructGenericDataList!("secondSublist", 
MyBinarySubStructBForA));
}

...

MyBinaryStructA *binaryData = cast(MyBinaryStructA 
*)fileData.ptr;

...

Yes, there is definately no other way but to use string mixins 
here, however if you switch to a mixin template, and put the 
string mixin inside of that, you don't have to do text 
replacement to use the template parameters.

Example:
mixin template GenericDataList(string name, T)
{
    mixin(`
        int `~name~`SublistCount;
        int `~name~`SublistOffset;

        @property auto `~name~`Sublist()
        {
            return (cast(T*)(cast(byte*)&this + 
`~name~`SublistOffset))[0..`~name~`SublistCount];
        }`);
}

struct MyBinarySubStructAForA
{
    int someIntegerFieldA;
    float someFloatFieldA;
}

struct MyBinarySubStructBForA
{
    int someIntegerFieldB;
    float someFloatFieldB;
}

struct MyBinaryStructA
{
    mixin MyBinaryStructGenericDataList!("first", 
MyBinarySubStructAForA);
    mixin MyBinaryStructGenericDataList!("second", 
MyBinarySubStructBForA);
}