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Linking math.h definitions

When you include the math.h in C programming file then also when we are using GCC and trying to compile it show the error that the which you have used from math.h is not defined. Example Assume if you had used pow function in you C program file then it will show an error undefined symbol pow. The reason behind this is in math.h there are only prototypes but it is defined in libm file which we can link by using -lm option while using GCC command to compile you C file.

#libm #math.h

How to: Why do you have to link the math library in C?

Why do you have to link the math library in C?

If I include <stdlib.h> or <stdio.h> in a C program I don’t have to link these when compiling but I do have to link to <math.h>, using -lm with gcc, for example:

gcc test.c -o test -lm

What is the reason for this? Why do I have to explicitly link the math library but not the other libraries?

Answer: Why do you have to link the math library in C?

st…

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#c #compilation #math.h

Math functions and constants

Today few math functions and constants available in Objective-C.

They are included in the math.h header. It's available into the iOS/OS X SDK.

MATH FUNCTIONS

pow(double, double) - power of

NSLog(@"%.f", pow(3,2) ); //result 9 NSLog(@"%.f", pow(3,3) ); //result 27

sqrt(double) - square root

NSLog(@"%.f", sqrt(16) ); //result 4 NSLog(@"%.f", sqrt(81) ); //result 9

ceil(double) - the next bigger integer

NSLog(@"res: %.f", ceil(3.000000000001)); //result 4 NSLog(@"res: %.f", ceil(3.00)); //result 3

floor(double) - removes the decimal part

NSLog(@"res: %.f", floor(3.000000000001)); //result 3 NSLog(@"res: %.f", floor(3.9999999)); //result 3

round(double) - rounds the argument

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

fmin(double, double) - the smaller

NSLog(@"res: %.f", fmin(5,10)); //result 5 NSLog(@"res: %.f", MIN(5,10)); //result 5

fmax(double, double) - the bigger

NSLog(@"res: %.f", fmax(5,10)); //result 10 NSLog(@"res: %.f", MAX(5,10)); //result 10

fabs(double) - the absolute value

NSLog(@"res: %.f", fabs(10)); //result 10 NSLog(@"res: %.f", fabs(-10)); //result 10 other functions to get the absolute value are described here

MATH CONSTANTS

M_E 2.71828182845904523536028747135266250 /* e */ M_LOG2E 1.44269504088896340735992468100189214 /* log 2e */ M_LOG10E 0.434294481903251827651128918916605082 /* log 10e */ M_LN2 0.693147180559945309417232121458176568 /* log e2 */ M_LN10 2.30258509299404568401799145468436421 /* log e10 */ M_PI 3.14159265358979323846264338327950288 /* pi */ M_PI_2 1.57079632679489661923132169163975144 /* pi/2 */ M_PI_4 0.785398163397448309615660845819875721 /* pi/4 */ M_1_PI 0.318309886183790671537767526745028724 /* 1/pi */ M_2_PI 0.636619772367581343075535053490057448 /* 2/pi */ M_2_SQRTPI 1.12837916709551257389615890312154517 /* 2/sqrt(pi) */ M_SQRT2 1.41421356237309504880168872420969808 /* sqrt(2) */ M_SQRT1_2 0.707106781186547524400844362104849039 /* 1/sqrt(2) */ MAXFLOAT ((float)3.40282346638528860e+38)

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