Evaluates Carlson’s elliptic integral of the first kind RF(x, y, z).

x—First argument for which the function value is desired. It must be nonnegative.

y—Second argument for which the function value is desired. It must be nonnegative.

z—Third argument for which the function value is desired. It must be nonnegative.

result—The complete elliptic integral RF(x, y, z).

Double—If present and nonzero, double precision is used.

Carlson’s elliptic integral of the second kind is defined to be:

The arguments must be nonnegative and less than or equal to b/5. In addition, x + y, x + z, and y + z must be greater than or equal to 5s. Should any of these conditions fail, ELRF is set to b. Here, b is the largest and is the smallest representable number.

The function ELRF is based on the code by Carlson and Notis (1981) and the work of Carlson (1979).

The integral RF(0, 1, 2) is computed.

PRINT, ELRF(0.0, 1.0, 2.0)

; PV-WAVE prints: 1.31103