longsub.prg

用VFP计算平方根(例如sqtr(2))到6万5千位小数的程序.

* longsub.prg
* 长减法
* 注意：此程序未考虑最高位的借位问题，
* 因为这实际不可能发生
parameters a,b
private except eachlen,alllen
*eachlen=10
*alllen=len(a)
n=alllen/eachlen
c=""
jiewei=0
for i=1 to n step 1
   *@ 8,10 say "longsub减法已做"+str(i)+"遍"
   point1=alllen-i*eachlen+1
   sub_a=substr(a,point1,eachlen)
   sub_b=substr(b,point1,eachlen)
   if sub_a>=sub_b
      num_c=val(sub_a)-val(sub_b)-jiewei
      jiewei=0
   else
      num_c=10**eachlen+val(sub_a)-val(sub_b)-jiewei
      jiewei=1
   endif
   sub_c=str(num_c,eachlen+1)
   sub_c=chrtran(sub_c," ","0")
   sub_c=right(sub_c,eachlen)
   c=sub_c+c
next i
return c