function?erf?=?ErrFunc（x）
format?long;
pi?=?3.1415926535;
m?=?1;
tol?=?1;
while?tol?>?1.0e-6
????s1?=?subERF（xm）;
????s2?=?subERF（xm+1）;
????tol?=?abs（s1?-?s2）;
????