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D - operator <type> () ?

reply "Achilleas Margaritis" <axilmar in.gr> writes:
C++ has a type of function which is used in implicit conversions: operator
<type> (). By using this type of function, one type of object can be
implicitly converted to another type of object. Does D have something
similar (which I can't find in the docs) ?

If not, does Walter plan to do it ? is there an alternative ? For me, it is
quite useful, as I can define value structs which are implicitly converted
to something when as that something. For example, an RGB struct is
implicitly converted to int when used as int, producing a pixel value for
the current graphics context.
Apr 28 2004
next sibling parent reply J Anderson <REMOVEanderson badmama.com.au> writes:
Achilleas Margaritis wrote:

C++ has a type of function which is used in implicit conversions: operator
<type> (). By using this type of function, one type of object can be
implicitly converted to another type of object. Does D have something
similar (which I can't find in the docs) ?

  
No there is no such thing in D.
If not, does Walter plan to do it ? is there an alternative ? 
I doubt Walter will implement anything like this as it goes against his design principals. That's why D doesn't have a copy-constructor.
For me, it is
quite useful, as I can define value structs which are implicitly converted
to something when as that something. For example, an RGB struct is
implicitly converted to int when used as int, producing a pixel value for
the current graphics context.
Parhaps you could just wrap the graphics context up (pseudo): ie void putPixel(RGB c, int x, int y) { putPixel((int)c, x, y);} void putPixel(int c, int x, int y) { dc[x+y*height] = c; } Or write a generic conversion function like so: template covT(T1, T2) { T2 cov(T1 t) { return *(cast(T2*) &t); } } struct RGBA { byte R,G,B,A; } alias covT!(int, RGBA).cov cov; alias covT!(RGBA, int).cov cov; void func(int c) { } int main ( char [] [] args ) { RGBA c; int ic = cov(c); RGBA irgba = cov(ic); func(cov(c)); return 1; } -- -Anderson: http://badmama.com.au/~anderson/
Apr 28 2004
parent Stewart Gordon <smjg_1998 yahoo.com> writes:
J Anderson wrote:

 Achilleas Margaritis wrote:
<snip>
 For me, it is quite useful, as I can define value structs which are implicitly 
 converted to something when as that something. For example, an RGB struct is
 implicitly converted to int when used as int, producing a pixel value for
 the current graphics context.
Parhaps you could just wrap the graphics context up (pseudo): ie
<snip> I tend to use unions for this kind of stuff. e.g. union RGBA { struct { byte r, g, b, a; } int value; } Then you only need to define each function once. You can add an opCall to the union to make it easy to construct. See D/25334 Stewart. -- My e-mail is valid but not my primary mailbox, aside from its being the unfortunate victim of intensive mail-bombing at the moment. Please keep replies on the 'group where everyone may benefit.
Apr 30 2004
prev sibling next sibling parent Juan C <Juan_member pathlink.com> writes:
<snip>
C++ has a type of function which is used in implicit conversions: operator
<type> (). By using this type of function, one type of object can be
</snip> Ew. Implicit conversions (casts) should only be allowed between like types (e.g. among integer types, among real types, etc.) and of course only when no data is lost. As such I am against implicit conversion to boolean, which I feel is most evil. You should consider a property, like RGB.intValue or something, even make it a setter as well as a getter.
Apr 28 2004
prev sibling parent "Matthew" <matthew.hat stlsoft.dot.org> writes:
"Achilleas Margaritis" <axilmar in.gr> wrote in message
news:c6p61u$1c5j$1 digitaldaemon.com...
 C++ has a type of function which is used in implicit conversions: operator
 <type> (). By using this type of function, one type of object can be
 implicitly converted to another type of object. Does D have something
 similar (which I can't find in the docs) ?

 If not, does Walter plan to do it ? is there an alternative ? For me, it is
 quite useful, as I can define value structs which are implicitly converted
 to something when as that something. For example, an RGB struct is
 implicitly converted to int when used as int, producing a pixel value for
 the current graphics context.
D's not going to have them. There are other approaches. How about some Shims (http://www.cuj.com/documents/s=8681/cuj0308wilson/), for example? You might not like it because it's a new buzzword, tho ... ;)
Apr 29 2004