colon operator bug?

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Can Atalay
Can Atalay 2022-4-2
回答： Can Atalay 2022-4-3
Is creating an array by saying;
x = 1:5;
not robust? Because
x(3)
returned something like
3.0001221
And I got an
Array indices must be positive integers or logical values.
error when trying to index into another array using my "x".
I can share the real script (which is pretty long) and the files (1+ GB) but wanted to ask the simpler version first. If the colon operator for sure works perfect I should probably go spend some more time before posting
  1 个评论
Riccardo Scorretti
Riccardo Scorretti 2022-4-2
编辑：Riccardo Scorretti 2022-4-2
Ran in:
There is no reason to observe the described behaviour. By the way, I cannot reproduce:
x = 1:5;
format long ; x(3)
ans =
3
Are you sure there isn't something else? -- I mean, some code between the definition of x and x(3)?

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采纳的回答

Can Atalay
Can Atalay 2022-4-3
My bad, turns out I changed a for loop index inside that for loop and appended the index it to an array, and the index turned out not functioning like an integer somehow.
Fixed itself when I corrected the index names - we can delete the question if you guys want

更多回答（1 个）

Jan
Jan 2022-4-2
The colon operator works as expected. For integer values it does reply integers. But be aware of rounding effects for floating point values:
a = 0:0.1:1
any(a == 0.3) % FALSE!
See FAQ: Why is 0.1+0.2~=0.3
  2 个评论
Riccardo Scorretti
Riccardo Scorretti 2022-4-2
Exact, because 0.1 is periodic in base 1. But here, it should not be the case.
Stephen23
Stephen23 2022-4-2
编辑：Stephen23 2022-4-2
"because 0.1 is periodic in base 1"
Can you please show us 0.1 written in base 1. Or any fractional number in base 1, for that matter.
"But here, it should not be the case."
Which is more likely:
  • COLON has a major bug which thousands and thousands of users never noticed.
  • The OP's code does not do what they think it is doing.

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