cpp/numeric/special functions/comp ellint 1

@1-3@ Computes the of. @A@ Additional overloads are provided for all integer types, which are treated as.

Return value
If no errors occur, value of the complete elliptic integral of the first kind of, that is , is returned.

Error handling
Errors may be reported as specified in math_errhandling.
 * If the argument is NaN, NaN is returned and domain error is not reported.
 * If $|k|>1$, a domain error may occur.