6868
6969 </ head >
7070 < body >
71- < header data-kunai-mdinfo ="{"meta": {"header": ["optional"], "namespace": ["std"], "class": ["optional"], "id-type": ["function"], "cpp": ["cpp26"]}, "sources": [{"id": "0e9914a5a89a8df5a4751094875ee0f90b43d490 ", "source": "#include <iostream>\n#include <optional>\n\nint main()\n{\n std::optional<int> p1 = 1;\n for (auto i = p1.begin(); i != p1.end(); ++i) {\n std::cout << *i; // \uff11\u5ea6\u901a\u308b\n }\n\n std::optional<int> p2 = std::null_opt ;\n for (auto i = p2.begin(); i != p2.end(); ++i) {\n std::cout << *i; // \uff11\u5ea6\u3082\u901a\u3089\u306a\u3044\n }\n}\n"}], "page_id": ["reference", "optional", "optional", "begin"]} ">
71+ < header data-kunai-mdinfo ="{"meta": {"header": ["optional"], "namespace": ["std"], "class": ["optional"], "id-type": ["function"], "cpp": ["cpp26"]}, "sources": [{"id": "57a3988e5f8bd704cd38b12bb2b7e5126cd91a69 ", "source": "#include <iostream>\n#include <optional>\n\nint main()\n{\n std::optional<int> p1 = 1;\n for (auto i = p1.begin(); i != p1.end(); ++i) {\n std::cout << *i; // \uff11\u5ea6\u901a\u308b\n }\n\n std::optional<int> p2 = std::nullopt ;\n for (auto i = p2.begin(); i != p2.end(); ++i) {\n std::cout << *i; // \uff11\u5ea6\u3082\u901a\u3089\u306a\u3044\n }\n}\n"}], "page_id": ["reference", "optional", "optional", "begin"]} ">
7272 < nav class ="navbar navbar-default " role ="navigation ">
7373 < div class ="container-fluid ">
7474 < div class ="navbar-header ">
200200
201201 < p class ="text-right "> < small >
202202 最終更新日時(UTC):
203- < span itemprop ="datePublished " content ="2025-11-12T11:34:03 ">
204- 2025年11月12日 11時34分03秒
203+ < span itemprop ="datePublished " content ="2026-03-23T08:00:07 ">
204+ 2026年03月23日 08時00分07秒
205205 </ span >
206206 < br />
207207 < span itemprop ="author " itemscope itemtype ="http://schema.org/Person ">
208- < span itemprop ="name "> suomesta </ span >
208+ < span itemprop ="name "> Raclamusi </ span >
209209 </ span >
210210 が更新
211211 </ small > </ p >
@@ -235,7 +235,7 @@ <h2>効果</h2>
235235< p > < code > < a href ="has_value.html "> has_value()</ a > == true</ code > なら、保持している有効値を指すイテレータを返す。またこの時、< code > < a href ="../../iterator/distance.html "> distance</ a > (begin(), < a href ="end.html "> end()</ a > ) == 1</ code > となる。</ p >
236236< p > < code > < a href ="has_value.html "> has_value()</ a > != true</ code > なら、末尾要素の次を指すイテレータを返す。この時、< code > begin() == < a href ="end.html "> end()</ a > </ code > である。</ p >
237237< h2 > 例</ h2 >
238- < p > < div class ="yata " id ="0e9914a5a89a8df5a4751094875ee0f90b43d490 "> < div class ="codehilite "> < pre > < span > </ span > < code > < span class ="cp "> #include < a href ="../../iostream.html "> <iostream></ a > </ span >
238+ < p > < div class ="yata " id ="57a3988e5f8bd704cd38b12bb2b7e5126cd91a69 "> < div class ="codehilite "> < pre > < span > </ span > < code > < span class ="cp "> #include < a href ="../../iostream.html "> <iostream></ a > </ span >
239239< span class ="cp "> #include < a href ="../../optional.html "> <optional></ a > </ span >
240240
241241< span class ="kt "> int</ span > < span class ="w "> </ span > < span class ="nf "> main</ span > < span class ="p "> ()</ span >
@@ -245,7 +245,7 @@ <h2>例</h2>
245245< span class ="w "> </ span > < span class ="n "> < a href ="../../iostream/cout.html "> std::cout</ a > </ span > < span class ="w "> </ span > < span class ="o "> <<</ span > < span class ="w "> </ span > < span class ="o "> *</ span > < span class ="n "> i</ span > < span class ="p "> ;</ span > < span class ="w "> </ span > < span class ="c1 "> // １度通る</ span >
246246< span class ="w "> </ span > < span class ="p "> }</ span >
247247
248- < span class ="w "> </ span > < span class ="n "> < a href ="../optional.html "> std::optional</ a > </ span > < span class ="o "> <</ span > < span class ="kt "> int</ span > < span class ="o "> ></ span > < span class ="w "> </ span > < span class ="n "> p2</ span > < span class ="w "> </ span > < span class ="o "> =</ span > < span class ="w "> </ span > < span class ="n "> std</ span > < span class ="o "> ::</ span > < span class ="n "> null_opt </ span > < span class ="p "> ;</ span >
248+ < span class ="w "> </ span > < span class ="n "> < a href ="../optional.html "> std::optional</ a > </ span > < span class ="o "> <</ span > < span class ="kt "> int</ span > < span class ="o "> ></ span > < span class ="w "> </ span > < span class ="n "> p2</ span > < span class ="w "> </ span > < span class ="o "> =</ span > < span class ="w "> </ span > < span class ="n "> std</ span > < span class ="o "> ::</ span > < span class ="n "> nullopt </ span > < span class ="p "> ;</ span >
249249< span class ="w "> </ span > < span class ="k "> for</ span > < span class ="w "> </ span > < span class ="p "> (</ span > < span class ="k "> auto</ span > < span class ="w "> </ span > < span class ="n "> i</ span > < span class ="w "> </ span > < span class ="o "> =</ span > < span class ="w "> </ span > < span class ="n "> p2</ span > < span class ="p "> .</ span > < span class ="n "> < span style ="color:#ff0000 "> begin()</ span > </ span > < span class ="p "> ;</ span > < span class ="w "> </ span > < span class ="n "> i</ span > < span class ="w "> </ span > < span class ="o "> !=</ span > < span class ="w "> </ span > < span class ="n "> p2</ span > < span class ="p "> .</ span > < span class ="n "> < a href ="end.html "> end()</ a > </ span > < span class ="p "> ;</ span > < span class ="w "> </ span > < span class ="o "> ++</ span > < span class ="n "> i</ span > < span class ="p "> )</ span > < span class ="w "> </ span > < span class ="p "> {</ span >
250250< span class ="w "> </ span > < span class ="n "> < a href ="../../iostream/cout.html "> std::cout</ a > </ span > < span class ="w "> </ span > < span class ="o "> <<</ span > < span class ="w "> </ span > < span class ="o "> *</ span > < span class ="n "> i</ span > < span class ="p "> ;</ span > < span class ="w "> </ span > < span class ="c1 "> // １度も通らない</ span >
251251< span class ="w "> </ span > < span class ="p "> }</ span >
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