# Why is \`=\` no function **URL:** \ **Category:** Internals & Design\ **Tags:** question\ **Created:** [September 26, 2020, 10:03am UTC](https://discourse.julialang.org/t/why-is-no-function/47304 "2020-09-26T10:03:09Z")\ **Posts on this page:** 7\ **Page:** 2

**Author:** ![tomerarnon](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tomerarnon/32/3170_2.png) [@tomerarnon](https://discourse.julialang.org/u/tomerarnon)\ **Post date:** [September 28, 2020, 11:58am UTC](https://discourse.julialang.org/t/why-is-no-function/47304/22 "2020-09-28T11:58:39Z")

Sure it can 😅 Apologies for the screenshot, I just googled “i = 1, 2…” to find the first example. ![Screen Shot 2020-09-28 at 2.52.24 PM](https://global.discourse-cdn.com/julialang/original/3X/2/9/2900b1d59d60e98d5a546acf4608f867f73d7f3a.png) Surely the above represents that i is 1, then it is 2, and so forth until `k`, and is also clearly, and by far, the most natural aspect of the expression! So `i` can be reassigned at will 😄 For context, my first language was R (and there was a two year eternity before I learned another…), and I did not find myself using the `<-` assignment operator even once. I found it extremely unnatural from the beginning, while repeatedly assigning the same variable did not seem unusual to me at all. So likely, this all amounts very strongly to a matter of taste. ---

**Author:** ![remi-garcia](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/remi-garcia/32/7125_2.png) [@remi-garcia](https://discourse.julialang.org/u/remi-garcia)\ **Post date:** [September 28, 2020, 12:07pm UTC](https://discourse.julialang.org/t/why-is-no-function/47304/23 "2020-09-28T12:07:38Z")

No it cannot 😛 This notation is, at least to me, wrong. `i` is not equal to multiple values, it is `in`. The best would have been: ```tex i \in \left\[\!\left[1, k\right]\right] ``` See [Interval (mathematics) - Wikipedia](https://en.wikipedia.org/wiki/Interval_(mathematics)#Integer_intervals) For your screenshot: I just don’t get why someone would mixed up notations. `1 ... k` means nothing, while `{1 ... k}`, although not perfect, would have been better and consistent with `{p \in D [...]}` Yet, I agree with you. I learned R (not as my first language) and avoided `<-`. In fact I think that @Tamas_Papp is right, `<-` should be avoided and it should be clearly stated that `=` is not the mathematical equality. ---

**Author:** ![Tamas\_Papp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamas_papp/32/25949_2.png) [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\ **Post date:** [September 28, 2020, 12:15pm UTC](https://discourse.julialang.org/t/why-is-no-function/47304/24 "2020-09-28T12:15:19Z")

> [@remi-garcia](#): > > I learned R (not as my first language) and avoided `<-` . I don’t think you can. Only at the toplevel. FWIW, I have heard two justifications for `<-` in R: 1. there is a version that _goes the other way_. Eg 2. Consistency with `<<-` and its evil twin `->>`. This is not an issue for Julia as it has no equivalent, because it subscribed to a model of scope other than “kitchen sink”, a fact that we should really appreciate. ---

**Author:** ![tomerarnon](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tomerarnon/32/3170_2.png) [@tomerarnon](https://discourse.julialang.org/u/tomerarnon)\ **Post date:** [September 28, 2020, 12:34pm UTC](https://discourse.julialang.org/t/why-is-no-function/47304/25 "2020-09-28T12:34:06Z")

> [@remi-garcia](#): > > This notation is, at least to me, wrong. I considered addressing this in advance, but opted against ultimately. Yes, you could say this should be written otherwise, but the point is it is perfectly clear and unambiguous. `=`, like all other symbols, is merely notation, and just like its use in that equation is perfectly clear (everyone seems to read `i = 1, ..., k` “correctly”), the assignment operator in code is also clear an unambiguous. `a = 1; a = 2;` can have only one meaning. > [@Tamas\_Papp](#): > > I don’t think you can. Only at the toplevel. I’m tempted to disagree because I’m pretty sure I _did_, but it’s been long enough that I’m not confident in that anymore… ---

**Author:** ![remi-garcia](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/remi-garcia/32/7125_2.png) [@remi-garcia](https://discourse.julialang.org/u/remi-garcia)\ **Post date:** [September 28, 2020, 12:50pm UTC](https://discourse.julialang.org/t/why-is-no-function/47304/26 "2020-09-28T12:50:32Z")

> [@tomerarnon](#): > > the point is it is perfectly clear and unambiguous I don’t know, I think we (or only I?) just naturally translate this notation into something that is correct. But it’s like `{a real : a < s_i for i = [1,5]]`. Everything is “wrong” here and the fact that you get the point (e.g. by correcting the last `]` with `}` or by understanding that `i` is an integer) doesn’t make it right. That’s to say that I get that students can be frustrated by the “abuse of notation” that we use when programming. But @Tamas_Papp solved it to me: I should not try to teach the concept without `=` but rather define this new use of the equality and stick with it. > [@tomerarnon](#): > > > [@Tamas\_Papp](#): > > > > I don’t think you can. Only at the toplevel. > > I’m tempted to disagree because I’m pretty sure I _did_ , but it’s been long enough that I’m not confident in that anymore… Same as @tomerarnon, maybe I used `<-` in R and concealed it deep in my memory. @Impressium Sorry for the digression, I wanted to ask a quick question and that led to an interesting disagreement 🙂 Edit: for the context, I barely started teaching (no lectures, just exercises) so I am interested in tips on this kind of basic concepts, thus my initial question. ---

**Author:** ![AleMorales](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/alemorales/32/48720_2.png) [@AleMorales](https://discourse.julialang.org/u/AleMorales)\ **Post date:** [October 20, 2020, 8:02am UTC](https://discourse.julialang.org/t/why-is-no-function/47304/27 "2020-10-20T08:02:42Z")

> [@Tamas\_Papp](#): > > I don’t think you can. Only at the toplevel. Maybe not that important but, you can use `=` everywhere in R and the R documentation is subtly wrong (or just confusing). For example, `system.time({a = rnorm(1e6)})` or `system.time((a = rnorm(1e6)))` works and is the same as `system.time(a <- rnorm(1e6))`. I think this has to do with brackets creating a subexpression and then `=` is interpreted as an assignment rather than a syntactical token for named arguments inside function calls… the kind of “feature” that can create a lot of silent bugs… ---

**Author:** ![sashmit](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/sashmit/32/18791_2.png) [@sashmit](https://discourse.julialang.org/u/sashmit)\ **Post date:** [October 20, 2020, 8:08pm UTC](https://discourse.julialang.org/t/why-is-no-function/47304/28 "2020-10-20T20:08:31Z")

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