mirror of
https://github.com/ultimatepp/ultimatepp.git
synced 2026-06-18 14:15:22 -06:00
61 lines
No EOL
3.1 KiB
C++
61 lines
No EOL
3.1 KiB
C++
topic "Transfer semantics";
|
|
[2 $$0,0#00000000000000000000000000000000:Default]
|
|
[l288;i704;a17;O9;~~~.992;2 $$1,0#10431211400427159095818037425705:param]
|
|
[a83;*R6 $$2,5#31310162474203024125188417583966:caption]
|
|
[b83;*2 $$3,5#07864147445237544204411237157677:title]
|
|
[b167;a42;C2 $$4,6#40027414424643823182269349404212:item]
|
|
[b42;a42;2 $$5,5#45413000475342174754091244180557:text]
|
|
[l288;a17;2 $$6,6#27521748481378242620020725143825:desc]
|
|
[l321;t246;C@5;1 $$7,7#20902679421464641399138805415013:code]
|
|
[b2503;2 $$8,0#65142375456100023862071332075487:separator]
|
|
[*@(0.0.255)2 $$9,0#83433469410354161042741608181528:base]
|
|
[t4167;C2 $$10,0#37138531426314131251341829483380:class]
|
|
[l288;a17;*1 $$11,11#70004532496200323422659154056402:requirement]
|
|
[i417;b42;a42;O9;~~~.416;2 $$12,12#10566046415157235020018451313112:tparam]
|
|
[b167;C2 $$13,13#92430459443460461911108080531343:item1]
|
|
[i288;a42;O9;C2 $$14,14#77422149456609303542238260500223:item2]
|
|
[*@2$(0.128.128)2 $$15,15#34511555403152284025741354420178:NewsDate]
|
|
[l321;*C$7;2 $$16,16#03451589433145915344929335295360:result]
|
|
[l321;b83;a83;*C$7;2 $$17,17#07531550463529505371228428965313:result`-line]
|
|
[l160;t4167;*C+117 $$18,5#88603949442205825958800053222425:package`-title]
|
|
[{_}%EN-US
|
|
[s2; Transfer semantics&]
|
|
[s3; Explicit pick/clone&]
|
|
[s5; U`+`+ containers require the transfer mode (deep copy or move)
|
|
to be explicitly specified when transfering the content of the
|
|
container (exception is the temporary value, which can be pick
|
|
assigned without explicit pick). This decision has the advantage
|
|
of not accidentally using costly deep copy semantics, when in
|
|
reality move is required in majority of case..&]
|
|
[s7; Vector<int> a, b;&]
|
|
[s7; a `= pick(b); // moves content of b to a, b is cleared&]
|
|
[s7; b `= clone(a); // a and b now contain the same data&]
|
|
[s5; &]
|
|
[s3; Composition&]
|
|
[s5; When class contains members with pick semantics, a lot of error`-prone
|
|
work is saved when compiler is able to generate pick constructor/operator`=
|
|
for the class. C`+`+11 is quite capable of doing so, but needs
|
|
to explicitly activate it with default memebers:&]
|
|
[s7; Foo(Foo`&`&) `= default;&]
|
|
[s7; Foo`& operator`=(Foo`&`&) `= default;&]
|
|
[s5; Meanwhile, C`+`+03 does need these and does not recognize them.
|
|
To make things easier, we define macro rval`_default, which simplifies
|
|
this and irons out differences&]
|
|
[s7; rval`_default(Foo)&]
|
|
[s3; Optional deep copy `- clone, uniform access to deep copy&]
|
|
[s5; To support clone, class has to define special constructor of
|
|
form&]
|
|
[s7; T(const T`&, int)&]
|
|
[s5; and to derive from DeepCopyOption<T> class, which provides support
|
|
for static/dynamic construction of instances.&]
|
|
[s3; Changing default semantics&]
|
|
[s5; If for some reason you need version of [/ optional] deep copy
|
|
type with [/ default] deep copy, you can easily create it with
|
|
[* WithDeepCopy ]template&]
|
|
[s7; IntArray a `= MakeArray(100);&]
|
|
[s7; WithDeepCopy<IntArray> b(a); // b now has deep copy semantics&]
|
|
[s7; a`[3`] `= 10; //legal&]
|
|
[s7; b `= a; // deep copy&]
|
|
[s7; a `= pick(b); // pick&]
|
|
[s7; b`[4`] `= 1; // illegal&]
|
|
[s0; ]] |