Wait, are those examples real?
I remember complaining about 1-bsaed indexing only to be told "julia is great! we have offsetindex". If it's a source of bugs, that ... greatly reduces my future interest in adopting the language.
I remember complaining about 1-bsaed indexing only to be told "julia is great! we have offsetindex". If it's a source of bugs, that ... greatly reduces my future interest in adopting the language.
I would still think most of this is my failings, but it is also extraordinarily hard to figure out what is going wrong.
When I looked at the adjoint event handling code last, I couldn’t figure out in the implementation, whether the general case was handled correctly, especially since parts of it still seemed in flux. Writing similar code in JAX leaves close to no room for interpretation that the code is correct. I am sure most of it is down to familiarity. But since ultimately I want to do ML relared things, right now JAX and related libraries ties up things that are there much more neatly even though overall SciML implements a more comprehensive set of techniques. I am still closely following the work around it especially in the area I am interested in and have some prototypes written in it, but it just hasn’t clicked yet.
> struct Element{T, Unit} <: Number > value::T > end
which is placed in the array.
It can be a source of bugs because some/many packages incorrectly assume that what you pass is 1-based indexed.
> OffsetArrays in particular proved to be a strong source of correctness bugs. The package provides an array type that leverages Julia’s flexible custom indices feature to create arrays whose indices don’t have to start at zero or one.
Array indexing is such a core thing and I don't understand why anything mathematical or scientific would start with 1.
0 makes sense as the '0-th offset' when thinking from a pointer perspective, but I often find when teaching, that 1-based comes more naturally for many students (the 'first' item).
You mention mathematical or scientific work...but I often/mainly see enumerations (such as weights x_1, x_2, ... x_n or SUM 1 to N) start with 1, so for these 1-based can be a more natural/direct translation of mathematical notation to code.
Math textbooks and papers tend to use 1-based subscripts when it doesn't matter. It's hard to come up with examples where starting at 1 facilitates the actual math.
I came to 0-based offsets later in my career, having started with Matlab. So I have some real experience with 1-based offsets. Experience that was 'untainted' by being used to a different option. I much prefer 0-based.
Especially because I now sort-off have a linter rule in my head 'if I am writing i - 1 then I am making a mistake or doing something the wrong way'. Which has been quite successful.
Because that's how maths work? Literally everywhere in maths you count from 1, except in software engineering. That's why. I hope that clarified your confusion.
What index to start with only strongly matters when the indexes have semantics. Otherwise you should just treat it as an opaque index, i.e. eachindex(), keys(), etc. In math when there are semantics, the indices usually include 0. When not (vector components, matrix indices, etc), they usually (but not uniformly) don't.
The one nice side-benefit of Julia's mistake in adopting 1-based indexing is that it provided an extra impetus to build machinery to handle arbitrary indexing, though too much code still doesn't work correctly, and code still gets written to only handle 1-based arrays.
Which in everyday computing (as opposed to mathematics) they often do, and those cases are (most?) often, in human terms, much more natural to start from 1: "I have an array of N elements. The first of a bunch of things is thing number one, and the last of N things is thing number N." Hence:
N_things: Array[1-N] of Thing;
for i := 1 to N do begin
Whatever := Whatever + Whateverize(N_things[i]);
end; // for i := 1 to N...
> The one nice side-benefit of Julia's mistake in adopting 1-based indexing is that it provided an extra impetus to build machinery to handle arbitrary indexing
1) Arguably, as per the above, not a mistake.
2) Muahaha, "build machinery"? No need to build anything new; that's already existed since the early 70s. (Yeah, that's how old I am: Not adding 19 in front. There was only one "the seventies".) It's not like starting at 1 was mandatory; you could well declare
My_fifty_things: Array[19-68] of Thing;
(At least in Turbo, but AFAICR also in original Wirth Pascal. Though probably with the max-255-ASCII-elements limitation in Wirth, and possibly also in Turbo up to v. 2 or 3 or so.)
__
[1]: Though from at least Turbo Pascal 3 (probably earlier; also think I saw it on some minicomputer implementation) with the backdoor of changing the length by directly manipulating -- surprise, surprise, it exists! String was a built-in type with its own implementation -- the length bit at index [0]. Better start out with your string declared as length 255, though, so you don't accidentally try to grow it beyond what's allocated.
This meaning of natural is highly cultural dependent. It took the Greeks a startlingly long time to accept that one was a number (because it's a singleton), much less zero. I do not e.g. want arrays that can't have length one, because they have to be containing a number of things.
> No need to build anything new;
Well, no, not "new". Arrays with arbitrary bounds is a well-trod path. But they still had to make it work in Julia: CartesianIndices, LinearIndices, and overloading of "begin", and "end" keywords, etc. And the radical dependence on multimethod dispatch meant they couldn't quite just reuse existing work from other languages.
> In math when there are semantics, the indices usually include 0
Complete nonsense. For example, in a Laurent expansion you start in the negatives and go up. Now you're gonna say "but that's an exception, I said _usually_". But it's not, this is the general case.
From data analytic point of view, indexing should start with 1. When we analyze a data table, we always call the first row as the 1st row, or row #1, not row #0. It will be very strange to label rows as 0, 1, 2, 3, .... It may be fine for people with Computer Science background. But it would create so much confusion for almost everyone else...
Having said that, given that there are basements (in Europe, at least), it makes sense to call the ground floor 0. We are dealing with integers here, not natural numbers.
How many other such examples can you (editorial you; anyone) come up with? Not many, I'd bet.
- Hours after midnight. The (non-anglosaxon) watch goes from 0:00 to 24:00 (the latter is useful for deadlines: The proposal must be submitted by Friday, 24:00 (which coincides with Saturday, 0:00)).
Then I cheated and looked up Wikipedia (https://en.wikipedia.org/wiki/Zero-based_numbering#Other_fie... ) - and whoops, that's basically it!
And I should know; the alarm clock on my windowsill says 0:54 right now.
But this is perhaps more of a problem with numbers and zeroes, and ends and beginnings; people don't get that 10 is the last of the 00s, not the first of the 10s. The very first year was numbered 1, not 0, so that's not the problem. Or, it kind of is: People would be right, if the first year had been 0.
So, no FORTRAN, huh?
Because starting with 0 is neither math nor array indexing in general.
It's just how the base addresss of an array pointer memory block was referenced in C (and it spread from there).
Which is why all math focused languages use 1-based (fortran, apl, matlab, r, mathematica, etc.)
BCPL.
It very, very much is. Polynomials all start at a zero "index", as does just about every expansion I can think of (Fourier, Bessel, Legendre, Chebyshev, Spherical Harmonic, etc.) Combinatorics, too, make lots of use of zero indices and zero-sized sets. As for arrays, I'll leave it to Dijkstra[1] to explain why zero indexing is most natural. Zero indexing overwhelmingly makes the most sense in both math and computers because indexing is a different operation than counting.
[1]: https://www.cs.utexas.edu/users/EWD/transcriptions/EWD08xx/E...
Notice how you had to put index in quotes.
Because it's not an index, it's the degree of each polynomial term, which is a power.
When the argument is:
[0] is very, very much is [natural for indexes]
Polynomials all start at a zero "index"
Notice also how there's no ad-hominen in my response (this or the previous one) as you claim. I argue against the case and the choice of example, not against who wrote it.
(For more than you ever wanted to know about this, The Ad Hominem Fallacy Fallacy covers it exhaustively and entertainingly:
> Notice how you had to put index in quotes.
as the thrust of the argument. In saying that, they imply that I, the arguer, 'A' in Bond's article, don't actually know what an index is (so how could I have a cogent argument about 'correct' indexing?). As this is the only argument of merit, it seems as though OP is actually trying to counter the point by suggesting (attacking) something of the arguer (myself).
Now, it may be that this ad homenim is justified -- if I truly don't know what an index is then yes, I probably should not be making claims about them -- but it's still an ad homenim (and, possibly, poor form).
Of course, this is ascribing a lot to 25 words of text with little other context. I would be interested to understand if you see things differently/think I have grossly erred in my analysis.
That's not what they are saying. They are saying you know what an index is so well that you correctly put quotes around your usage of the term, because you understood it's not in fact a technically correct usage.
Now calling an argument poor form... that's closer to ad hominem.
Yes. That's addressing the point you made.
Ad hominem would be: "You're a bad person/you have this or that flaw/etc (unrelated personal stuff)".
This is: "You put the index in quotes, because even you know that this is not an index. And in any case, this is not considered an index in math, it's a degree, which is a different thing".
I also didn't "merely offered another term", as if I made up some term on my own, or just offered on of several equal alternatives. Instead, I gave the correct math term for the thing described.
>In saying that, they imply that I, the arguer, 'A' in Bond's article, don't actually know what an index is (so how could I have a cogent argument about 'correct' indexing?).
It would rather imply the opposite: that you know what an index is, and you know that the thing you applied it to, is not an index (which is why it was put in scare quotes).
There was also the famous 1-pager by Dijkstra: "Why numbering should start at zero"
There are many similar path-dependent conventions in human culture. E.g. percentages originated before the concept of decimal fractions, base-sixty time units come from ancient Mesopotamia, and conventions about multi-dimensional array memory layout are based on the convention for drawing matrices on paper.
Most common mathematical sequences and series work better (more naturally/clearly) when zero indexing is used instead, and off-by-1 errors are a problem in mathematics just like computing (but less of a problem, because notation errors get silently corrected in readers’ heads, and don’t actually have to be interpreted strictly).
For indices: indices are about referencing elements of finite ordered sets, say of size N. Hence the 'abstract' indexing set for N elements is the ordinal N. The most canonical way to represent it is to take the length-N prefix of the natural numbers (eg 0-based indexing, von neumann ordinals), which happen to have all sorts of additional structure (eg mod-N arithmetic). This is also consistent with the offset view (the i-th element is at offset i). The fact that people tend to start ordinal numbers at 1 doesn't change anything that mathematicians working with ordinal numbers take them to start at 0, for the same reason we start naturals at 0.
See also: notation for higher derivatives https://arxiv.org/abs/1801.09553; a bit further but in the same vein: notations for free variables in programs as de-bruijn indices (or some variant thereof) (it's further because it's practical for doing proofs, but not for writing concrete terms). There are probably other instances.
When dealing with matrices and vectors (including data tables and data columns), there is a strong preference for 1 based indexing: first row, first column, first entry, etc. Most matrix and vector based algorithms in literature use 1 based indexing. Programming these in a language with 0 based indexing is a mess, and a common source or errors.
When dealing with sequences, especially recursively defined ones, there is usually an initial value (indexed with 0) and then the n-th value is obtained by n applications of the recursive step, so 0 based indexing makes more sense, but in literature there is no fixed convention, and you can find examples with 0 based and with 1-based indexing. Another example of 0 based indexing in math are polynomials (and in extension, power series) where the index is the degree of the term, or in general any functional series where the 0-th term is the constant term.
There are also negative indices.
Counting things is such a core thing to humans that when we have a bunch of N things we think of them as thing #1 to thing #N. We start counting from 1, not 0.
Indexing from 0 in computing is adapting the human mind to the computer, purely for performance reasons that may have been relevant in the 50s or 60s but were beginning to be obsolete by the 70s. It was done so you could access elements of an array by the simplest possible calculation of your offset into heap memory. When your first element is stored at Starting_address, you need i for that first element to be = 0, just so you don't need to have the compiler add another constant term for each element to "Element is at Starting_address + i * sizeof(element)".
Would have been trivial, even then (as Wirth showed) to add that constant term calculation to compilers, but it was done without in C because that eliminated one whole integer operation from each (set of?) array access(es).
In stead, we got the mental gymnastics of
for(i=0, i++, i<=N-1) {...}
While preferring one over the other is perfectly fine, I question the intellectual honesty of anyone claiming incredulity about opposite choice.
Try doing a block iteration over an array, or any kind of interval algorithms in 0-based and 1-based. 0-based with right-open intervals just results in way way more elegant, easier to understand and (very) slightly more efficient code.
Just think about what you're saying: that natural language usage of the word "first" is wrong, and doing things the opposite way that everyone expects in programming languages is somehow more understandable? Really? Maybe that makes perfect sense to you, but not to people using the word as it's commonly used.
If humans had got this right then we wouldn't be even having this discussion. Same for similar mistakes like Pi vs Tau, negative electrons. But the mistake is understandable given that we didn't even think of 0 for a long time.
Dijkstra's argument as well hinges on an undefined notion of "ugliness", which can mean anything to anyone. That's why these conversations never end, because most people are talking past one another based on their own definitions of "elegance" or "ugliness".
Nobody has any trouble in the UK with lifts where the ground floor is 0 - one of the few places where humans got it right.
That’s certainly a perspective.
If you say so! Maybe you should start a foundation to encourage humanity to change its counting behaviour. The effective altruists might throw you a couple of million.
For some reason, people who are used to 1-based indexing generally recognize that both interpretations are perfectly fine, and that each works well in different contexts. For some other reason, people used to 0-based indexing feel so intellectually superior that they are unable to see the other side of the argument.
You must have warped your brain into thinking like a computer (well, a C-family-language compiler) for so long and/or so thoroughly that you no longer think quite like an ordinary human.
Having to sprinkle semi-arbitrary "-1"s all over your code is in no reasonable sense of the words "way way more elegant, easier to understand" than not having to do so.