You know how from time to time, you want to have an array which you can
access via:
array_name[element];
But also, you'd like the more user-friendly option:
array_name.elem ent1
array_name.elem ent2
I believe that some people use a union with an anonymous struct for this
(which is not legal Standard C++) as follows:
union Week
{
unsigned days[7];
struct
{
unsigned monday;
unsigned tuesday;
... //and so on
};
} christmas_week;
Well firstly, even if anonymous structs *were* legal, the above code would
still not necessarily work as expected - to be specific, "tuesday" doesn't
necessarily have the same address as days[1], and why? padding.
So... the following is my way of doing it. The only drawback is that it's no
longer an aggreagate nor a POD:
struct Week
{
unsigned days[7];
unsigned &monday;
unsigned &tuesday;
... //and so on
Week() : monday( days[0] ), tuesday( days[1] ) //and so on
};
-JKop 5 2730
"JKop" <NU**@NULL.NULL > wrote in message
news:1x******** ***********@new s.indigo.ie... You know how from time to time, you want to have an array which you can access via:
array_name[element];
But also, you'd like the more user-friendly option:
array_name.elem ent1 array_name.elem ent2
[SNIP]
Whether the second option is more userfriendly is arguable. However, you
could use a map with strings as keys if you deem this more legible or
user-friendly.
Chris
Good work. However, your struct will probably require twice as much
memory as the union solution.
Also, padding shouldn't be a problem with ints, but there certainly is
no definite way to tell.
BTW, why is anonymous structs illegal in unions ? Will allowing it
create any specific problem ?
-Arijit
JKop <NU**@NULL.NULL > wrote in message news:<1x******* ************@ne ws.indigo.ie>.. . You know how from time to time, you want to have an array which you can access via:
array_name[element];
But also, you'd like the more user-friendly option:
array_name.elem ent1 array_name.elem ent2
I believe that some people use a union with an anonymous struct for this (which is not legal Standard C++) as follows:
union Week { unsigned days[7];
struct { unsigned monday; unsigned tuesday; ... //and so on }; } christmas_week;
Well firstly, even if anonymous structs *were* legal, the above code would still not necessarily work as expected - to be specific, "tuesday" doesn't necessarily have the same address as days[1], and why? padding.
So... the following is my way of doing it. The only drawback is that it's no longer an aggreagate nor a POD:
struct Week { unsigned days[7];
unsigned &monday; unsigned &tuesday; ... //and so on
Week() : monday( days[0] ), tuesday( days[1] ) //and so on };
-JKop
"Arijit" <pa*****@yahoo. co.in> wrote in message
news:df******** *************** **@posting.goog le.com... Good work. However, your struct will probably require twice as much memory as the union solution.
Also, padding shouldn't be a problem with ints, but there certainly is no definite way to tell.
BTW, why is anonymous structs illegal in unions ? Will allowing it create any specific problem ?
Anonymous structs are not legal at all, in unions or otherwise.
john
John Harrison wrote: Anonymous structs are not legal at all, in unions or otherwise.
There's not even a definition of that term. But if you take the
C++ defintion of anonymous union and replace union with struct,
it isn't legal.
JKop wrote: So... the following is my way of doing it. The only drawback is that it's no longer an aggreagate nor a POD:
Nice, but the other drawback is that it's twice the size of
the original structure.
struct Week { unsigned days[7];
unsigned &monday; unsigned &tuesday; ... //and so on
Week() : monday( days[0] ), tuesday( days[1] ) //and so on }; This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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