在实际工作中有些程序不可避免的需要使用数学函数进行计算,比如地图程序的地理坐标到地图坐标的变换。Objective-C做为ANSI C的扩展,使用C标准库头文件<math.h>中定义的数学常量宏及数学函数来实现基本的数学计算操作,所以不必费神再在Cocoa Foundation中寻找相应的函数和类了。这里列出一些常用宏和数学函数,更详细的信息还是需要去查阅<math.h>头文件。 数学常量: #define M_E 2.71828182845904523536028747135266250 // e #define M_LOG2E 1.44269504088896340735992468100189214 // log 2e #define M_LOG10E 0.434294481903251827651128918916605082 // log 10e #define M_LN2 0.693147180559945309417232121458176568 // log e2 #define M_LN10 2.30258509299404568401799145468436421 // log e10 #define M_PI 3.14159265358979323846264338327950288 // pi #define M_PI_2 1.57079632679489661923132169163975144 // pi/2 #define M_PI_4 0.785398163397448309615660845819875721 // pi/4 #define M_1_PI 0.318309886183790671537767526745028724 // 1/pi #define M_2_PI 0.636619772367581343075535053490057448 // 2/pi #define M_2_SQRTPI 1.12837916709551257389615890312154517 // 2/sqrt(pi) #define M_SQRT2 1.41421356237309504880168872420969808 // sqrt(2) #define M_SQRT1_2 0.707106781186547524400844362104849039 // 1/sqrt(2) 常用函数: //指数运算 NSLog(@"%.f", pow(3,2) ); //result 9 NSLog(@"%.f", pow(3,3) ); //result 27 //开平方运算 NSLog(@"%.f", sqrt(16) ); //result 4 NSLog(@"%.f", sqrt(81) ); //result 9 //上舍入 NSLog(@"res: %.f", ceil(3.000000000001)); //result 4 NSLog(@"res: %.f", ceil(3.00)); //result 3 //下舍入 NSLog(@"res: %.f", floor(3.000000000001)); //result 3 NSLog(@"res: %.f", floor(3.9999999)); //result 3 //四舍五入 NSLog(@"res: %.f", round(3.5)); //result 4 NSLog(@"res: %.f", round(3.46)); //result 3 NSLog(@"res: %.f", round(-3.5)); //NB: this one returns -4 //最小值 NSLog(@"res: %.f", fmin(5,10)); //result 5 //最大值 NSLog(@"res: %.f", fmax(5,10)); //result 10 //绝对值 NSLog(@"res: %.f", fabs(10)); //result 10 NSLog(@"res: %.f", fabs(-10)); //result 10