目录搜索
AlgorithmsAlgorithms(算法)bsearchbsearch_sqsortqsort_sAtomic operationsAtomic operations library(原子操作库)ATOMIC_*_LOCK_FREEatomic_compare_exchange_strongatomic_compare_exchange_strong_explicitatomic_compare_exchange_weakatomic_compare_exchange_weak_explicitatomic_exchangeatomic_exchange_explicitatomic_fetch_addatomic_fetch_add_explicitatomic_fetch_andatomic_fetch_and_explicitatomic_fetch_oratomic_fetch_or_explicitatomic_fetch_subatomic_fetch_sub_explicitatomic_fetch_xoratomic_fetch_xor_explicitatomic_flagatomic_flag_clearatomic_flag_clear_explicitATOMIC_FLAG_INITatomic_flag_test_and_setatomic_flag_test_and_set_explicitatomic_initatomic_is_lock_freeatomic_loadatomic_load_explicitatomic_signal_fenceatomic_storeatomic_store_explicitatomic_thread_fence(线程围栏)ATOMIC_VAR_INITkill_dependencymemory_order(内存排序)C keywordsauto(自动存储)break(跳出循环)C keywords(关键词)casecharconst(常量修饰符)continuedefault(预设运算式)dodouble(双精度浮点型)elseenum(枚举类型)extern(全局变量)float(浮点数)forfortrangoto(goto语句)if(if语句)inline(行内函式)intlong(长整型)register(寄存器变量)restrict( restrict类型限定符)returnshortsignedsizeof(sizeof运算符)static(静态变量)struct(结构体)switch(switch语句)typedef(typedef关键字)union(联合体)unsigned(无符号)void(空类型)volatile(volatile变量)while(while语句)_Alignas_Alignof_Atomic_Bool_Complex_Generic_Imaginary_Noreturn_Static_assert_Thread_localC language#define directive#elif directive#else directive#endif directive#error directive#if directive#ifdef directive#ifndef directive#include directive#line directive#pragma directivealignas(对齐指定符)Alternative operators and tokens(替代运算符和令牌)AnalyzabilityArithmetic operatorsArithmetic typesArray declaration(数组声明)Array initialization(阵列初始化)ASCII ChartAssignment operators(赋值运算符)types(atomic类型限定符)Basic conceptsBit fields(位域)break statementC languageC Operator Precedencecast operatorcharacter constant(字符字面量)Comments(注释符)Comparison operators(比较运算符)compound literals(符合字面量)Conditional inclusion(条件包含)Conformance(一致性)const type qualifier(const 限定符)Constant expressions(常量表达)continue statementDeclarations(声明)do-while loopEnumerations(枚举类型)Escape sequences(转义字符)Expressions(表达式)External and tentative definitions(外部和暂定的定义)File scope(文件范围)floating constant(浮点常量)for loopFunction declarations(函数声明)Function definitions(函数声明)FunctionsGeneric selection泛型选择goto statementIdentifier(标示符)if statementImplicit conversions(隐式转换)Increment/decrement operators(前置/后置操作符)Initialization(初始化)inline function specifier(内联函式)integer constantLifetime(生命期)Logical operators(逻辑运算符)Lookup and name spacesMain function(主函式)Member access operators(会员接入运营商)Memory modelObjects and alignment(字节对齐)Order of evaluation(评估顺序)Other operatorsPhases of translation(翻译阶段)Pointer declarationPreprocessor(预处理)restrict type qualifier(restrict类型限定符)return statementScalar initialization(标量类型初始化)Scope(范围)sizeof operator(sizeof运算符)Statements(陈述)static assert declaration(静态断言声明)Static storage duration(静态存储周期)Storage-class specifiers(存储类说明符)string literals(字符串字面量)Struct and union initialization(结构体与联合体初始化)Struct declaration(结构体声明)switch statementThread storage duration(线程存储时间)TypeType(类型)Typedef declaration(Typedef声明)Undefined behavior(未定义行为)Union declaration(联合体声明)Value categories(值类别)Variadic arguments(变长参数宏)volatile type qualifier(volatile 类型限定符)while loop_Alignof operator_Noreturn function specifierDate and timeasctime(asctime函数)asctime_sclockCLOCKS_PER_SECclock_tctime(ctime函数)ctime_sDate and time utilities(日期和时间库)difftime(计算两个时间的间隔)gmtimegmtime_slocaltimelocaltime_smktime(将时间结构数据转换成经过的秒数的函数)strftime(格式化输出时间函数)timetimespectimespec_gettime_ttmwcsftime(格式化时间宽字符)Dynamic memory managementaligned_allocC memory management library(内存管理库)callocfree(释放动态分配空间的函数)malloc(动态分配内存空间的函数)realloc(重新分配内存空间的函数)Error handlingabort_handler_sassert(断言)constraint_handler_terrno(错误报告)Error handling(错误处理)Error numbers(错误个数)ignore_handler_sset_constraint_handler_sstatic_assertFile input/outputclearerr(清除/复位)fclosefeofferrorfflush(清空文件缓冲区)fgetcfgetposfgetsfgetwcfgetwsFile input/outputfopenfopen_sfprintffprintf_sfputcfputsfputwcfputwsfreadfreopenfreopen_sfscanffscanf_sfseekfsetposftellfwidefwprintffwprintf_sfwritefwscanffwscanf_sgetcgetchargetsgets_sgetwcharperrorprintfprintf_sputcputcharputsputwcputwcharremoverenamerewindscanfscanf_ssetbufsetvbufsnprintfsprintfsscanfsscanf_sswprintfswprintf_sswscanfswscanf_stmpfiletmpfile_stmpnamtmpnam_sungetcungetwcvfprintfvfprintf_svfscanfvfscanf_svfwprintfvfwprintf_svfwscanfvfwscanf_svprintfvprintf_svscanfvscanf_svsnprintfvsprintfvsscanfvsscanf_svswprintfvswprintf_svswscanfvswscanf_svwprintfvwprintf_svwscanfvwscanf_swprintfwprintf_swscanfwscanf_sLocalization supportlconvLC_ALLLC_COLLATELC_CTYPELC_MONETARYLC_NUMERICLC_TIMElocaleconvLocalization supportsetlocaleNumericsabsacosacosfacoshacoshfacoshlacoslasinasinfasinhasinhfasinhlasinlatanatan2atan2fatan2latanfatanhatanhfatanhlatanlcabscabsfcabslcacoscacosfcacoshcacoshfcacoshlcacoslcargcargfcarglcasincasinfcasinhcasinhfcasinhlcasinlcatancatanfcatanhcatanhfcatanhlcatanlcbrtcbrtfcbrtlccosccosfccoshccoshfccoshlccoslceilceilfceillcexpcexpfcexplcimagcimagfcimaglclogclogfcloglCMPLXCMPLXFCMPLXLCommon mathematical functionscomplexComplex number arithmeticconjconjfconjlcopysigncopysignfcopysignlcoscosfcoshcoshfcoshlcoslcpowcpowfcpowlcprojcprojfcprojlcrealcrealfcreallcsincsinfcsinhcsinhfcsinhlcsinlcsqrtcsqrtfcsqrtlctanctanfctanhctanhfctanhlctanldivdouble_terferfcerfcferfclerfferflexpexp2exp2fexp2lexpfexplexpm1expm1fexpm1lfabsfabsffabslfdimfeclearexceptfegetenvfegetexceptflagfegetroundfeholdexceptferaiseexceptfesetenvfesetexceptflagfesetroundfetestexceptfeupdateenvFE_ALL_EXCEPTFE_DFL_ENVFE_DIVBYZEROFE_DOWNWARDFE_INEXACTFE_INVALIDFE_OVERFLOWFE_TONEARESTFE_TOWARDZEROFE_UNDERFLOWFE_UPWARDFloating-point environmentfloat_tfloorfloorffloorlfmafmaffmalfmaxfmaxffmaxlfminfminffminlfmodfmodffmodlfpclassifyFP_INFINITEFP_NANFP_NORMALFP_SUBNORMALFP_ZEROfrexpfrexpffrexplHUGE_VALHUGE_VALFHUGE_VALLhypothypotfhypotlIilogbilogbfilogblimaginaryimaxabsimaxdivINFINITYisfiniteisgreaterisgreaterequalisinfislessislessequalislessgreaterisnanisnormalisunorderedlabsldexpldexpfldexplldivlgammalgammaflgammalllabslldivllrintllrintfllrintlllroundllroundfllroundlloglog10log10flog10llog1plog1pflog1pllog2log2flog2llogblogbflogbllogflogllrintlrintflrintllroundlroundflroundlMATH_ERREXCEPTmath_errhandlingMATH_ERRNOmodfmodffmodflnanNANnanfnanlnearbyintnearbyintfnearbyintlnextafternextafterfnextafterlnexttowardnexttowardfnexttowardlNumericspowpowfpowlPseudo-random number generationrandRAND_MAXremainderremainderfremainderlremquoremquofremquolrintrintfrintlroundroundfroundlscalblnscalblnfscalblnlscalbnscalbnfscalbnlsignbitsinsinfsinhsinhfsinhlsinlsqrtsqrtfsqrtlsrandtantanftanhtanhftanhltanltgammatgammaftgammaltrunctruncftrunclType-generic math_Complex_I_Imaginary_IProgram supportabortatexitat_quick_exitexitEXIT_FAILUREEXIT_SUCCESSgetenvgetenv_sjmp_buflongjmpProgram support utilitiesquick_exitraisesetjmpSIGABRTSIGFPESIGILLSIGINTsignalSIGSEGVSIGTERMsig_atomic_tSIG_DFLSIG_ERRSIG_IGNsystem_ExitStringsatofatoiatolatollbtowcc16rtombc32rtombchar16_tchar32_tisalnumisalphaisblankiscntrlisdigitisgraphislowerisprintispunctisspaceisupperiswalnumiswalphaiswblankiswcntrliswctypeiswdigitiswgraphiswloweriswprintiswpunctiswspaceiswupperiswxdigitisxdigitmblenmbrlenmbrtoc16mbrtoc32mbrtowcmbsinitmbsrtowcsmbsrtowcs_smbstate_tmbstowcsmbstowcs_smbtowcmemchrmemcmpmemcpymemcpy_smemmovememmove_smemsetmemset_sNull-terminated byte stringsNull-terminated multibyte stringsNull-terminated wide stringsstrcatstrcat_sstrchrstrcmpstrcollstrcpystrcpy_sstrcspnstrerrorstrerrorlen_sstrerror_sStrings librarystrlenstrncatThread supportcall_oncecnd_broadcastcnd_destroycnd_initcnd_signalcnd_timedwaitcnd_waitmtx_destroymtx_initmtx_lockmtx_plainmtx_recursivemtx_timedmtx_timedlockmtx_trylockmtx_unlockonce_flagONCE_FLAG_INITthrd_busythrd_createthrd_currentthrd_detachthrd_equalthrd_errorthrd_exitthrd_jointhrd_nomemthrd_sleepthrd_successthrd_timedoutthrd_yieldThread support librarythread_localtss_createtss_deleteTSS_DTOR_ITERATIONStss_gettss_setType supportBoolean type support libraryFixed width integer typesFLT_EVAL_METHODFLT_ROUNDSmax_align_tNULLNumeric limitsoffsetofptrdiff_tsize_tType supportVariadic functionsVariadic functionsva_argva_copyva_endva_listva_start
文字

在头文件<stdlib.h>中定义



float       ldexpf( float arg, int exp );

(1)

(since C99)

double      ldexp( double arg, int exp );

(2)


long double ldexpl( long double arg, int exp );

(3)

(since C99)

Defined in header <tgmath.h>



#define ldexp( arg, exp )

(4)

(since C99)

1-3)arg将数字2 的浮点值乘以exp功率。

4)类型 - 通用宏:如果arg有类型long doubleldexpl被调用。否则,如果arg有整数类型或类型doubleldexp则调用。否则ldexpf,分别称为。

参数

arg

-

浮点值

exp

-

整数值

返回值

如果没有错误发生,arg乘以2的幂exp(arg×2exp

)返回。

如果范围误差由于发生溢出,±HUGE_VAL±HUGE_VALF,或±HUGE_VALL返回。

如果发生下溢引起的范围错误,则返回正确的结果(舍入后)。

错误处理

按照math_errhandling中的指定报告错误。

如果实现支持IEEE浮点运算(IEC 60559),

  • 除非发生范围错误,否则FE_INEXACT不会引发(结果是确切的)

  • 除非发生范围错误,否则当前舍入模式将被忽略

  • 如果arg为±0,则返回,未修改

  • 如果arg是±∞,则返回,未修改

  • 如果exp为0,则arg返回,未修改

  • 如果arg是NaN,则返回NaN

笔记

二进制系统(其中,FLT_RADIX2),ldexp相当于scalbn

函数ldexp(“加载指数”)及其双数,frexp可以用来操纵浮点数的表示,而无需直接位操作。

在许多实现中,ldexp使用算术运算符的乘法或除法乘以二的幂的效率较低。

#include <stdio.h>#include <math.h>#include <float.h>#include <errno.h>#include <fenv.h>#pragma STDC FENV_ACCESS ON
int main(void){    printf("ldexp(7, -4) = %f\n", ldexp(7, -4));    printf("ldexp(1, -1074) = %g (minimum positive subnormal double)\n",            ldexp(1, -1074));    printf("ldexp(nextafter(1,0), 1024) = %g (largest finite double)\n",            ldexp(nextafter(1,0), 1024));    // special values    printf("ldexp(-0, 10) = %f\n", ldexp(-0.0, 10));    printf("ldexp(-Inf, -1) = %f\n", ldexp(-INFINITY, -1));    //error handling
    errno = 0; feclearexcept(FE_ALL_EXCEPT);    printf("ldexp(1, 1024) = %f\n", ldexp(1, 1024));    if(errno == ERANGE) perror("    errno == ERANGE");    if(fetestexcept(FE_OVERFLOW)) puts("    FE_OVERFLOW raised");}

可能的输出:

ldexp(7, -4) = 0.437500ldexp(1, -1074) = 4.94066e-324 (minimum positive subnormal double)ldexp(nextafter(1,0), 1024) = 1.79769e+308 (largest finite double)ldexp(-0, 10) = -0.000000ldexp(-Inf, -1) = -infldexp(1, 1024) = inf
    errno == ERANGE: Numerical result out of range
    FE_OVERFLOW raised

参考

  • C11标准(ISO / IEC 9899:2011):

    • 7.12.6.6 ldexp函数(p:244)

    • 7.25类型通用数学<tgmath.h>(p:373-375)

    • F.10.3.6 ldexp函数(p:522)

  • C99标准(ISO / IEC 9899:1999):

    • 7.12.6.6 ldexp函数(p:225)

    • 7.22类型通用数学<tgmath.h>(p:335-337)

    • F.9.3.6 ldexp函数(p:459)

  • C89 / C90标准(ISO / IEC 9899:1990):

    • 4.5.4.3 ldexp函数

上一篇:下一篇: