C++11中的stoi和stod怎么使用
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摘要：接下来，请跟着小编一起来学习吧！C++11的stoi & stod#include<iostream>include<string>usingnamespacestd;intmain(){stringstr="123";inta=stoi(str);//如果遇到非法输入，stoi会自动截取最前面的数字，知道遇到不是数字为止//所以说... ...
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接下来，请跟着小编一起来学习吧！
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c++11新特性集合
#C++11若想继续学习更多相关知识，请继续关注网站，小编会继续努力为大家带来更多实用的文章！Seealso:
std::move,std::forward,forwardingreferences.Templatetypeparameterdeductionwithlvaluesandrvalues:
Seealso:
std::move,std::forward,rvaluereferences.The
...syntaxcreatesa_parameterpack_orexpandsone.Atemplate_parameterpack_isatemplateparameterthatacceptszeroormoretemplatearguments(non-types,types,ortemplates).Atemplatewithatleastoneparameterpackiscalledavariadictemplate.Aninterestinguseforthisiscreatingan_initializerlist_froma_parameterpack_inordertoiterateovervariadicfunctionarguments.
Alightweightarray-likecontainerofelementscreatedusinga"bracedlist"syntax.Forexample,
{1,2,3}createsasequencesofintegers,thathastypestd::initializer_list<int>.Usefulasareplacementtopassingavectorofobjectstoafunction.Assertionsthatareevaluatedatcompile-time.
auto-typedvariablesarededucedbythecompileraccordingtothetypeoftheirinitializer.Extremelyusefulforreadability,especiallyforcomplicatedtypes:
Functionscanalsodeducethereturntypeusing
auto.InC++11,areturntypemustbespecifiedeitherexplicitly,orusingdecltypelikeso:Thetrailingreturntypeintheaboveexampleisthedeclaredtype(seesectionon
decltype)oftheexpressionx+y.Forexample,ifxisanintegerandyisadouble,decltype(x+y)isadouble.Therefore,theabovefunctionwilldeducethetypedependingonwhattypetheexpressionx+yyields.Noticethatthetrailingreturntypehasaccesstoitsparameters,andthiswhenappropriate.Bydefault,value-capturescannotbemodifiedinsidethelambdabecausethecompiler-generatedmethodismarkedas
const.Themutablekeywordallowsmodifyingcapturedvariables.Thekeywordisplacedaftertheparameter-list(whichmustbepresentevenifitisempty).
decltypeisanoperatorwhichreturnsthe_declaredtype_ofanexpressionpassedtoit.cv-qualifiersandreferencesaremaintainediftheyarepartoftheexpression.Examplesofdecltype:Seealso:
decltype(auto)(C++14).Semanticallysimilartousinga
typedefhowever,typealiaseswithusingareeasiertoreadandarecompatiblewithtemplates.C++11introducesanewnullpointertypedesignedtoreplaceC's
NULLmacro.nullptritselfisoftypestd::nullptr_tandcanbeimplicitlyconvertedintopointertypes,andunlikeNULL,notconvertibletointegraltypesexceptbool.Type-safeenumsthatsolveavarietyofproblemswithC-styleenumsincluding:implicitconversions,inabilitytospecifytheunderlyingtype,scopepollution.
Attributesprovideauniversalsyntaxover
__attribute__(...),__declspec,etc.Constantexpressionsareexpressionsevaluatedbythecompileratcompile-time.Onlynon-complexcomputationscanbecarriedoutinaconstantexpression.Usethe
constexprspecifiertoindicatethevariable,function,etc.isaconstantexpression.
constexprvaluesarethosethatthecompilercanevaluateatcompile-time:Constantexpressionswithclasses:
Constructorscannowcallotherconstructorsinthesameclassusinganinitializerlist.
User-definedliteralsallowyoutoextendthelanguageandaddyourownsyntax.Tocreatealiteral,definea
Toperator""X(...){...}functionthatreturnsatypeT,withanameX.Notethatthenameofthisfunctiondefinesthenameoftheliteral.Anyliteralnamesnotstartingwithanunderscorearereservedandwon'tbeinvoked.Therearerulesonwhatparametersauser-definedliteralfunctionshouldaccept,accordingtowhattypetheliteraliscalledon.ConvertingCelsiustoFahrenheit:
Stringtointegerconversion:
Specifiesthatavirtualfunctionoverridesanothervirtualfunction.Ifthevirtualfunctiondoesnotoverrideaparent'svirtualfunction,throwsacompilererror.
Specifiesthatavirtualfunctioncannotbeoverriddeninaderivedclassorthataclasscannotbeinheritedfrom.
Classcannotbeinheritedfrom.
Amoreelegant,efficientwaytoprovideadefaultimplementationofafunction,suchasaconstructor.
Withinheritance:
Amoreelegant,efficientwaytoprovideadeletedimplementationofafunction.Usefulforpreventingcopiesonobjects.
Syntacticsugarforiteratingoveracontainer'selements.
Notethedifferencewhenusing
intasopposedtoint&:Thecopyconstructorandcopyassignmentoperatorarecalledwhencopiesaremade,andwithC++11'sintroductionofmovesemantics,thereisnowamoveconstructorandmoveassignmentoperatorformoves.
Convertingconstructorswillconvertvaluesofbracedlistsyntaxintoconstructorarguments.
Notethatthebracedlistsyntaxdoesnotallownarrowing:
Notethatifaconstructoracceptsa
std::initializer_list,itwillbecalledinstead:Conversionfunctionscannowbemadeexplicitusingthe
explicitspecifier.Allmembersofaninlinenamespacearetreatedasiftheywerepartofitsparentnamespace,allowingspecializationoffunctionsandeasingtheprocessofversioning.Thisisatransitiveproperty,ifAcontainsB,whichinturncontainsCandbothBandCareinlinenamespaces,C'smemberscanbeusedasiftheywereonA.
Allowsnon-staticdatamemberstobeinitializedwheretheyaredeclared,potentiallycleaningupconstructorsofdefaultinitializations.
C++11isnowabletoinferwhenaseriesofrightanglebracketsisusedasanoperatororasaclosingstatementoftypedef,withouthavingtoaddwhitespace.
Memberfunctionscannowbequalifieddependingonwhether
*thisisanlvalueorrvaluereference.C++11allowsfunctionsandlambdasanalternativesyntaxforspecifyingtheirreturntypes.
Thisfeatureisespeciallyusefulwhencertainreturntypescannotberesolved:
InC++14,
decltype(auto)canbeusedinstead.The
noexceptspecifierspecifieswhetherafunctioncouldthrowexceptions.Itisanimprovedversionofthrow().Non-throwingfunctionsarepermittedtocallpotentially-throwingfunctions.Wheneveranexceptionisthrownandthesearchforahandlerencounterstheoutermostblockofanon-throwingfunction,thefunctionstd::terminateiscalled.
Transferring
std::unique_ptrs:Anexampleofafunction
wrapperwhichjustforwardsotherAobjectstoanewAobject'scopyormoveconstructor:Seealso:
forwardingreferences,rvaluereferences.The
std::threadlibraryprovidesastandardwaytocontrolthreads,suchasspawningandkillingthem.Intheexamplebelow,multiplethreadsarespawnedtododifferentcalculationsandthentheprogramwaitsforallofthemtofinish.Convertsanumericargumenttoa
std::string.Typetraitsdefinesacompile-timetemplate-basedinterfacetoqueryormodifythepropertiesoftypes.
A
std::shared_ptrisasmartpointerthatmanagesaresourcethatissharedacrossmultipleowners.Asharedpointerholdsa_controlblock_whichhasafewcomponentssuchasthemanagedobjectandareferencecounter.Allcontrolblockaccessisthread-safe,however,manipulatingthemanagedobjectitselfisnotthread-safe.Thechronolibrarycontainsasetofutilityfunctionsandtypesthatdealwithdurations,clocks,andtimepoints.Oneusecaseofthislibraryisbenchmarkingcode:
Tuplesareafixed-sizecollectionofheterogeneousvalues.Accesstheelementsofa
std::tuplebyunpackingusingstd::tie,orusingstd::get.Createsatupleoflvaluereferences.Usefulforunpacking
std::pairandstd::tupleobjects.Usestd::ignoreasaplaceholderforignoredvalues.InC++17,structuredbindingsshouldbeusedinstead.
std::arrayisacontainerbuiltontopofaC-stylearray.Supportscommoncontaineroperationssuchassorting.Thecompilerisfreetocall
newT{},thenfunction_that_throws(),andsoon...SincewehaveallocateddataontheheapinthefirstconstructionofaT,wehaveintroducedaleakhere.Withstd::make_shared,wearegivenexception-safety:
std::ref(val)isusedtocreateobjectoftypestd::reference_wrapperthatholdsreferenceofval.Usedincaseswhenusualreferencepassingusing&doesnotcompileor&isdroppedduetotypededuction.std::crefissimilarbutcreatedreferencewrapperholdsaconstreferencetoval.
std::beginandstd::endfreefunctionswereaddedtoreturnbeginandenditeratorsofacontainergenerically.Thesefunctionsalsoworkwithrawarrayswhichdonothavebeginandendmemberfunctions.AnthonyCalandra
See:https://github.com/AnthonyCalandra/modern-cpp-features/graphs/contributors
MIT
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