Using M_PI with C89 standard

by

A conforming standard library file math.h is not only not required to, but actually must not define M_PI by default. In this context ‘by default’ means that M_PI must only get defined through compiler-specific tricks, most often undefined behavior through the use of reserved identifiers.

Just define the constant yourself (you can use the name M_PI freely, but should you want to be able to compile the code with a non-conforming compiler, you must first check that M_PI is not already defined). For convention’s sake, do not define M_PI as anything other than (the approximation of) pi.

More Related Contents:

  1. What is the behavior of integer division?
  2. Sum of the all the numbers between a and b [closed]
  3. How does C compute sin() and other math functions?
  4. Why should you use strncpy instead of strcpy?
  5. Variable declaration placement in C
  6. Rounding integer division (instead of truncating)
  7. Divide a number by 3 without using *, /, +, -, % operators
  8. Mapping a numeric range onto another
  9. Does either ANSI C or ISO C specify what -5 % 10 should be?
  10. How to use nan and inf in C?
  11. “undefined reference to `pow'” even with math.h and the library link -lm [duplicate]
  12. How do you print the EXACT value of a floating point number?
  13. Recursive declaration of function pointer in C
  14. Type to use to represent a byte in ANSI (C89/90) C?
  15. How to concatenate two integers in C
  16. Are floating point operations in C associative?
  17. Where can one find the C89/C90 standards in PDF format?
  18. Gaussian elimination without result for acceleration
  19. signed and unsigned arithmetic implementation on x86
  20. C variable declarations after function heading in definition [duplicate]
  21. Why does gdb evaluate sqrt(3) to 0?
  22. C: How to wrap a float to the interval [-pi, pi)
  23. sin, cos, tan and rounding error
  24. Intersection of two lines defined in (rho/theta ) parameterization
  25. Why is the behavior of the modulo operator (%) different between C and Ruby for negative integers?
  26. How to use % operator for float values in c
  27. Evaluate Mathematical Function from String [closed]
  28. Conditional tests in primality by trial division
  29. How sqrt() of GCC works after compiled? Which method of root is used? Newton-Raphson?
  30. Algorithm to pick values from array that sum closest to a target value?

Leave a Comment