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 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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
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在头文件<math.h>中定义 | ||
|---|---|---|
float remquof( float x, float y, int *quo ); | (1) | (since C99) |
double remquo( double x, double y, int *quo ); | (2) | (since C99) |
long double remquol( long double x, long double y, int *quo ); | (3) | (since C99) |
Defined in header <tgmath.h> | ||
#define remquo( x, y, quo ) | (4) | (since C99) |
1-3）x/y根据remainder()函数计算除法运算的浮点余数。此外，符号和至少三个最后的比特x/y将被存储在其中quo，足以确定一段时间内结果的八分之一。
4）类型 - 通用宏：如果任何非指针参数具有类型long double，remquol则被调用。否则，如果任何非指针参数具有整数类型或具有类型double，remquo则被调用。否则，remquof被调用。
参数
x,y | - | 浮点值 |
|---|---|---|
quo | - | 指向一个整数值的指针来存储符号和x / y的一些位 |
返回值
如果成功，则返回除法的浮点余x/y中定义remainder，并存储，在*quo，符号和至少三个的至少显著位x/y（正式地说，存储其符号是符号的值x/y，其大小是全等模2n
与x/y其中n是大于或等于3的实现定义的整数的整数商数的大小）。
如果y为零，则存储的值*quo未指定。
如果发生域错误，则返回实现定义的值（NaN，如果支持）。
如果由于下溢而发生范围错误，如果支持子正常则返回正确的结果。
如果y为零，但域错误不会发生，则返回零。
错误处理
按照math_errhandling中的指定报告错误。
如果y为零，则可能会出现域错误。
如果实现支持IEEE浮点运算（IEC 60559），
当前的舍入模式不起作用。
FE_INEXACT从未被提出如果
x是±∞并且y不是NaN，则返回并FE_INVALID提升NaN如果
y是±0并且x不是NaN，则返回并FE_INVALID提升NaN如果是
x或者y是NaN，则返回NaN
笔记
如果x是无限的或者y是零，POSIX要求发生域错误。
这个函数在实现周期函数时非常有用，该周期函数的周期可以精确地表示为一个浮点值：当计算一个非常大的sin（πx）时x，sin直接调用可能会导致大的错误，但是如果函数参数首先被减少remquo，可以使用商的低位比特来确定该周期内结果的符号和八分之一，而余数可以用于以高精度计算该值。
在某些平台上，该操作由硬件支持（例如，在Intel CPU上，FPREM1精确度仅为3位）。
例
#include <stdio.h>#include <math.h>#include <fenv.h>
#pragma STDC FENV_ACCESS ON
double cos_pi_x_naive(double x){
double pi = acos(-1); return cos(pi * x);}// the period is 2, values are (0;0.5) positive, (0.5;1.5) negative, (1.5,2) positivedouble cos_pi_x_smart(double x){
int quadrant;
double rem = remquo(x, 1, &quadrant);
quadrant = (unsigned)quadrant % 4; // keep 2 bits to determine quadrant
double pi = acos(-1); switch(quadrant) { case 0: return cos(pi * rem); case 1: return -cos(pi * rem); case 2: return -cos(pi * rem); case 3: return cos(pi * rem); };}int main(void){ printf("cos(pi * 0.25) = %f\n", cos_pi_x_naive(0.25)); printf("cos(pi * 1.25) = %f\n", cos_pi_x_naive(1.25)); printf("cos(pi * 1000000000000.25) = %f\n", cos_pi_x_naive(1000000000000.25)); printf("cos(pi * 1000000000001.25) = %f\n", cos_pi_x_naive(1000000000001.25)); printf("cos(pi * 1000000000000.25) = %f\n", cos_pi_x_smart(1000000000000.25)); printf("cos(pi * 1000000000001.25) = %f\n", cos_pi_x_smart(1000000000001.25)); // error handling feclearexcept(FE_ALL_EXCEPT);
int quo; printf("remquo(+Inf, 1) = %.1f\n", remquo(INFINITY, 1, &quo)); if(fetestexcept(FE_INVALID)) puts(" FE_INVALID raised");}可能的输出：
cos(pi * 0.25) = 0.707107cos(pi * 1.25) = -0.707107cos(pi * 1000000000000.25) = 0.707123cos(pi * 1000000000001.25) = -0.707117cos(pi * 1000000000000.25) = 0.707107cos(pi * 1000000000001.25) = -0.707107 remquo(+Inf, 1) = -nan FE_INVALID raised
参考
C11标准（ISO / IEC 9899：2011）：
7.12.10.3遥控功能（p：255）
7.25类型通用数学<tgmath.h>（p：373-375）
F.10.7.3遥控功能（p：529）
C99标准（ISO / IEC 9899：1999）：
7.12.10.3遥控功能（p：236）
7.22类型通用数学<tgmath.h>（p：335-337）
F.9.7.3遥控功能（p：465）