ATAN2PI (The GNU Fortran Compiler)

### 8.28 `ATAN2PI` — Circular arc tangent function ¶

Description:

  `ATAN2PI(Y, X)` computes {\rm {atan2}}(y, x) / \pi, and provides a measure of an angle in half-revolutions within the proper quadrant.

Standard:

  Fortran 2023

Class:

  Elemental function

Syntax:

  `RESULT = ATAN2PI(Y, X)`

Arguments:

  Y | The type shall be `REAL`.
  X | The type and kind type parameter shall be the same as Y. If Y is zero, then X shall be nonzero.

Return value:

  The return value has the same type and kind type parameter as Y and satisfies -1 \leq {\rm {atan2}}(y, x) / \pi \leq 1.

Example:

      program test_atan2pi
        real(kind=4) :: x = 1.e0_4, y = 0.5e0_4
        x = atan2pi(y, x)
      end program test_atan2pi

See also:

  `ACOSPI` — Circular arc cosine function
  `ASINPI` — Circular arc sine function
  `ATANPI` — Circular arc tangent function