Here is what may be happening here. You should be able to confirm this by looking at your compiler’s implementation of the pow function: Assuming you have the correct #include’s, (all the previous answers and comments about this are correct — don’t take the #include files for granted), the prototype for the standard pow function … Read more
This is a simple problem. You just forgot the semi colon at the end of your header file. The compiler errors you get for missing the semi colon at the end of a class definition are very hard to relate to the actual problem – just get in the habit of checking that when you … Read more
When it works, it’s because the calculation was done by the compiler itself (and included in the binary as if you wrote it out) printf(“8\n”); When it doesn’t work, is because the pow function is included in the math library and the math library isn’t linked with your binary by default. To get the math … Read more
I can see two reasons for doing it this way: firstly, the “fast invSqrt” method (really Newton Raphson) is now the method used in a lot of hardware, so this approach leaves open the possibility of taking advantage of such hardware (and doing potentially four or more such operations at once). This article discusses it … Read more
gcc can use builtin functions in many cases, their documentation says: Many of these functions are only optimized in certain cases; if they are not optimized in a particular case, a call to the library function is emitted. so therefore gcc will not need to link against the math library when using the builtin function … Read more
The functions in stdlib.h and stdio.h have implementations in libc.so (or libc.a for static linking), which is linked into your executable by default (as if -lc were specified). GCC can be instructed to avoid this automatic link with the -nostdlib or -nodefaultlibs options. The math functions in math.h have implementations in libm.so (or libm.a for … Read more
In C++, it’s always sufficient to use std::abs; it’s overloaded for all the numerical types. In C, abs only works on integers, and you need fabs for floating point values. These are available in C++ (along with all of the C library), but there’s no need to use them.
From school mathematics we know that the tangent has the definition tan(α) = sin(α) / cos(α) and we differentiate between four quadrants based on the angle that we supply to the functions. The sign of the sin, cos and tan have the following relationship (where we neglect the exact multiples of π/2): Quadrant Angle sin … Read more
The functions in stdlib.h and stdio.h have implementations in libc.so (or libc.a for static linking), which is linked into your executable by default (as if -lc were specified). GCC can be instructed to avoid this automatic link with the -nostdlib or -nodefaultlibs options. The math functions in math.h have implementations in libm.so (or libm.a for … Read more