问题描述
限时送ChatGPT账号..我对这段代码感到困惑:
I'm confused with this snippet of code:
t=0
while t<5: #currently loop runs for 10 seconds
print "in loop",t
if (t<5):
print "true"
t=t+0.01
在循环的最后一次运行中打印:
prints in the last run through of the loop:
in loop 5.0
true
现在,如果在最后一次通过循环时 t = 5.0 是真的,那么 t < 不应该是条件.5 在if 语句中不被满足?此外,它不应该甚至不运行 t=5 的循环,因为它也应该在 while 条件下失败吗?
Now if it is true that t = 5.0 on the last pass through the loop, shouldn't the condition that t < 5 in the if statement not be met? And furthermore, shouldn't it not even be running through the loop for t=5 since it should have also failed the while condition?
推荐答案
5 不一定是 5:
t=0
while t<5: #currently loop runs for 10 seconds
print "in loop",t, repr(t)
if (t<5):
print "true"
t=t+0.1
生产
in loop 0 0
true
in loop 0.1 0.1
true
in loop 0.2 0.2
true
in loop 0.3 0.30000000000000004
[...]
in loop 4.8 4.799999999999999
true
in loop 4.9 4.899999999999999
true
in loop 5.0 4.999999999999998
true
0.1 不能用二进制精确表示.
0.1 can't be represented exactly in binary.
[啊,我刚刚注意到我用的是 0.1 而不是 0.01,就像你一样.嗯,这是同样的问题.]
[Ah, I just noticed that I used 0.1 instead of 0.01, like you did. Well, it's the same issue.]
两个浮点工作原理"参考:经典 和 绅士.
Two "how floating point works" references: classical and gentler.
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