How can I write a power function myself?

by

Negative powers are not a problem, they’re just the inverse (1/x) of the positive power.

Floating point powers are just a little bit more complicated; as you know a fractional power is equivalent to a root (e.g. x^(1/2) == sqrt(x)) and you also know that multiplying powers with the same base is equivalent to add their exponents.

With all the above, you can:

  • Decompose the exponent in a integer part and a rational part.
  • Calculate the integer power with a loop (you can optimise it decomposing in factors and reusing partial calculations).
  • Calculate the root with any algorithm you like (any iterative approximation like bisection or Newton method could work).
  • Multiply the result.
  • If the exponent was negative, apply the inverse.

Example:

2^(-3.5) = (2^3 * 2^(1/2)))^-1 = 1 / (2*2*2 * sqrt(2))

More Related Contents:

  1. Integer division always zero [duplicate]
  2. How computer does floating point arithmetic?
  3. Is there any advantage to using pow(x,2) instead of x*x, with x double?
  4. How do I print a double value with full precision using cout?
  5. How does photoshop blend two images together? [closed]
  6. Finding all the subsets of a set
  7. Efficient implementation of log2(__m256d) in AVX2
  8. Direct way of computing clockwise angle between 2 vectors
  9. Should I use double or float?
  10. Why is my integer math with std::pow giving the wrong answer?
  11. Why isn’t `int pow(int base, int exponent)` in the standard C++ libraries?
  12. Floating point comparison revisited
  13. Building a 32-bit float out of its 4 composite bytes
  14. Rotate and translate object in local and global orientation using glm
  15. Fastest implementation of sine, cosine and square root in C++ (doesn’t need to be much accurate)
  16. Comparison of double, long double, float and float128?
  17. Math precision requirements of C and C++ standard
  18. Efficiently getting all divisors of a given number
  19. C: How to wrap a float to the interval [-pi, pi)
  20. Should we generally use float literals for floats instead of the simpler double literals?
  21. What is half open range and off the end value
  22. printf rounding behavior for doubles
  23. sin, cos, tan and rounding error
  24. C++ floating point to integer type conversions
  25. Check double variable if it contains an integer, and not floating point
  26. How to write a Float Mat to a file in OpenCV
  27. When a float variable goes out of the float limits, what happens?
  28. Why isn’t “0f” treated as a floating point literal in C++?
  29. Direct way of computing the clockwise angle between two vectors
  30. Fastest way to get the integer part of sqrt(n)?

Leave a Comment