谁能告诉我直接分解法和改进平方根法的C++程序代码

一个Fortran代码很容易改写为C++代码：
REAL FUNCTION SSQRT ( XSQ )

C *******************************************************************
C ** FUNCTION TO COMPUTE SQUARE ROOT FASTER THAN FORTRAN SQRT. **
C ** **
C ** THIS FUNCTION RETURNS THE SQUARE ROOT OF A REAL NUMBER XSQ **
C ** WITH 0.1 < XSQ < 1.0. THE METHOD USES A POLYNOMIAL **
C ** APPROXIMATION FOLLOWED BY NEWTON-RAPHSON ITERATION. **
C ** **
C ** REFERENCES: **
C ** **
C ** SINGER, CCP5 QUARTERLY, 8, 47, 1983. **
C ** POWLES, CCP5 QUARTERLY, 11, 39, 1984. **
C **