vfp编程具体操作
1+11+111+1111+11111....1111（50个1）=？
clear
c=replicate("1",50)
s=0
for i=1 to 50
s=s+val(substr(c,1,i))
endfor
?int(s)
2017-06-28 16:35
2017-06-28 16:47
2017-10-15 09:50
2017-10-15 10:06
