Re: Vim9: rethinking conditions and boolean expressions
> The "??" operator is used in TypeScript, JavaScript, C# and a few other > > languages. Oh ok, fair enough, thanks. Shows how much I know :) I’d never seen it before. > On 5 Oct 2020, at 14:20, Bram Moolenaar wrote: > > >>> var name = Getname() ?? 'unknown' >> >> This `??` operator seems a bit unique to vim9script. If we're trying to be >> more like other languages how about either re-using `else` (as in Getname() >> else 'unknown') or using `or` (Like python): `Getname() or "unknown"` > > Python operators are words, which I find making an expression harder to > understand. We don't have any operators that are words, I don't see a > reason to use it here. > > The "??" operator is used in TypeScript, JavaScript, C# and a few other > languages. > > -- > hundred-and-one symptoms of being an internet addict: > 35. Your husband tells you he's had that beard for 2 months. > > /// Bram Moolenaar -- b...@moolenaar.net -- http://www.Moolenaar.net \\\ > ///sponsor Vim, vote for features -- http://www.Vim.org/sponsor/ \\\ > \\\ an exciting new programming language -- http://www.Zimbu.org/// > \\\help me help AIDS victims -- http://ICCF-Holland.org/// -- -- You received this message from the "vim_dev" maillist. Do not top-post! Type your reply below the text you are replying to. For more information, visit http://www.vim.org/maillist.php --- You received this message because you are subscribed to the Google Groups "vim_dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to vim_dev+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/vim_dev/D96FFEAA-B17B-4CF5-BB68-2DD836329B24%40gmail.com.
Re: Vim9: rethinking conditions and boolean expressions
> > var name = Getname() ?? 'unknown' > > This `??` operator seems a bit unique to vim9script. If we're trying to be > more like other languages how about either re-using `else` (as in Getname() > else 'unknown') or using `or` (Like python): `Getname() or "unknown"` Python operators are words, which I find making an expression harder to understand. We don't have any operators that are words, I don't see a reason to use it here. The "??" operator is used in TypeScript, JavaScript, C# and a few other languages. -- hundred-and-one symptoms of being an internet addict: 35. Your husband tells you he's had that beard for 2 months. /// Bram Moolenaar -- b...@moolenaar.net -- http://www.Moolenaar.net \\\ ///sponsor Vim, vote for features -- http://www.Vim.org/sponsor/ \\\ \\\ an exciting new programming language -- http://www.Zimbu.org/// \\\help me help AIDS victims -- http://ICCF-Holland.org/// -- -- You received this message from the "vim_dev" maillist. Do not top-post! Type your reply below the text you are replying to. For more information, visit http://www.vim.org/maillist.php --- You received this message because you are subscribed to the Google Groups "vim_dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to vim_dev+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/vim_dev/202010051320.095DKXB62406083%40masaka.moolenaar.net.
Re: Vim9: rethinking conditions and boolean expressions
Dominique wrote: > Bram Moolenaar wrote: > > > For the first example, we can use a new operator which is specifically > > for testing an expression to be falsy and using a replacement: > > > > var name = Getname() ?? 'unknown' > > > > Let me know if you have comments. > > This is known as the 'elvis operator', which exists > in several languages. See: > > https://en.wikipedia.org/wiki/Elvis_operator > > Generally, it is ?: as in: > > var name = Getname() ?: 'unknown'; > > It may be worth saying that it is almost equivalent to > the longer: > > var name = Getname() ? Getname() : 'unknown'; > > ... except that in the case of the elvis operator, > Gename() is guaranteed to be invoked only once, > which may not only be more efficient, but can also > be different if Getname() had side effects. > > This image explains why it's called the 'elvis operator': > > https://i.stack.imgur.com/bVG64.png What I intend to do here makes a difference between the two operators, which is also why I prefer using "??" instead of "?:". The latter suggest the equivalence with "cond ? expr : expr", which is not quite right. The condition in "cond ? expr : expr" is just like a condition used for "if": it should evaluate to a boolean. The ternary expression is a short way of doing if-then-else, thus using the same semantics for the condition makes sense. For the "??" operator, which I prefer calling the falsy-operator, the expression is not required to evaluate to a boolean. In fact, it's most useful if it doesn't. It can be a string, list, dict, etc. And evaluating it will never result in an error, every value is either truthy or falsy. A name sometimes used is "nullish coalescing operator", which is not only hard to type but also not quite the same. "nullish" and "falsy" have different semantics. We could call it the "falsy coalescing operator", but "falsy operator" works just as well and is a lot easier to type. Still, "nullish coalescing operator" comes closest, thus using "??" as the operator will be recognized by most users. I hope the different semantics won't cause too much confusion. -- hundred-and-one symptoms of being an internet addict: 34. You laugh at people with a 10 Mbit connection. /// Bram Moolenaar -- b...@moolenaar.net -- http://www.Moolenaar.net \\\ ///sponsor Vim, vote for features -- http://www.Vim.org/sponsor/ \\\ \\\ an exciting new programming language -- http://www.Zimbu.org/// \\\help me help AIDS victims -- http://ICCF-Holland.org/// -- -- You received this message from the "vim_dev" maillist. Do not top-post! Type your reply below the text you are replying to. For more information, visit http://www.vim.org/maillist.php --- You received this message because you are subscribed to the Google Groups "vim_dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to vim_dev+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/vim_dev/202010051320.095DKWlx2406071%40masaka.moolenaar.net.
Re: Vim9: rethinking conditions and boolean expressions
Bram Moolenaar wrote: > For the first example, we can use a new operator which is specifically > for testing an expression to be falsy and using a replacement: > > var name = Getname() ?? 'unknown' > > Let me know if you have comments. This is known as the 'elvis operator', which exists in several languages. See: https://en.wikipedia.org/wiki/Elvis_operator Generally, it is ?: as in: var name = Getname() ?: 'unknown'; It may be worth saying that it is almost equivalent to the longer: var name = Getname() ? Getname() : 'unknown'; ... except that in the case of the elvis operator, Gename() is guaranteed to be invoked only once, which may not only be more efficient, but can also be different if Getname() had side effects. This image explains why it's called the 'elvis operator': https://i.stack.imgur.com/bVG64.png Regards Dominique -- -- You received this message from the "vim_dev" maillist. Do not top-post! Type your reply below the text you are replying to. For more information, visit http://www.vim.org/maillist.php --- You received this message because you are subscribed to the Google Groups "vim_dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to vim_dev+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/vim_dev/CAON-T_hAu7PD1%2Bx4LW8DZhTtrVf6j7FM%2BCKrKS1moqoTgHd29g%40mail.gmail.com.
Re: Vim9: rethinking conditions and boolean expressions
> var name = Getname() ?? 'unknown' This `??` operator seems a bit unique to vim9script. If we're trying to be more like other languages how about either re-using `else` (as in Getname() else 'unknown') or using `or` (Like python): `Getname() or "unknown"` On Sunday, October 4, 2020 at 10:47:15 PM UTC+1 Bram Moolenaar wrote: > > > In javascript you can use !! operator to always convert it to boolean. > > > > var name = '' > > var nameExists = !!(name || 'Prabir') > > Yes, and I think we should do the same. It should already work like > that now. > > Thus in most places where a condition is expected, such as with ":if" > and ":while", a boolean is expected. With legacy script you could use a > string, which was converted to a number and easily leads to mistakes. > Also numbers could be used. With Vim9 script only the numbers zero and > one can be used. This avoids making mistakes, but it's a bit strict. > > The new "??" operator can be used with any expression. Just like with > "!" accepts any expression. In these places the expression is tested to > be "falsy" or "truthy". > > I might have missed something, we might need a few more tests. > > > -- > hundred-and-one symptoms of being an internet addict: > 32. You don't know what sex three of your closest friends are, because they > have neutral nicknames and you never bothered to ask. > > /// Bram Moolenaar -- br...@moolenaar.net -- http://www.Moolenaar.net \\\ > /// sponsor Vim, vote for features -- http://www.Vim.org/sponsor/ \\\ > \\\ an exciting new programming language -- http://www.Zimbu.org /// > \\\ help me help AIDS victims -- http://ICCF-Holland.org /// > -- -- You received this message from the "vim_dev" maillist. Do not top-post! Type your reply below the text you are replying to. For more information, visit http://www.vim.org/maillist.php --- You received this message because you are subscribed to the Google Groups "vim_dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to vim_dev+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/vim_dev/b0bcb397-317c-4fa7-b42f-5ac6eebd3402n%40googlegroups.com.
Re: Vim9: rethinking conditions and boolean expressions
> In javascript you can use !! operator to always convert it to boolean. > > var name = '' > var nameExists = !!(name || 'Prabir') Yes, and I think we should do the same. It should already work like that now. Thus in most places where a condition is expected, such as with ":if" and ":while", a boolean is expected. With legacy script you could use a string, which was converted to a number and easily leads to mistakes. Also numbers could be used. With Vim9 script only the numbers zero and one can be used. This avoids making mistakes, but it's a bit strict. The new "??" operator can be used with any expression. Just like with "!" accepts any expression. In these places the expression is tested to be "falsy" or "truthy". I might have missed something, we might need a few more tests. -- hundred-and-one symptoms of being an internet addict: 32. You don't know what sex three of your closest friends are, because they have neutral nicknames and you never bothered to ask. /// Bram Moolenaar -- b...@moolenaar.net -- http://www.Moolenaar.net \\\ ///sponsor Vim, vote for features -- http://www.Vim.org/sponsor/ \\\ \\\ an exciting new programming language -- http://www.Zimbu.org/// \\\help me help AIDS victims -- http://ICCF-Holland.org/// -- -- You received this message from the "vim_dev" maillist. Do not top-post! Type your reply below the text you are replying to. For more information, visit http://www.vim.org/maillist.php --- You received this message because you are subscribed to the Google Groups "vim_dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to vim_dev+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/vim_dev/202010042147.094Ll6Gh2232566%40masaka.moolenaar.net.
Re: Vim9: rethinking conditions and boolean expressions
In javascript you can use !! operator to always convert it to boolean. var name = '' var nameExists = !!(name || 'Prabir') On Saturday, October 3, 2020 at 12:25:21 PM UTC-7 Andy Wokula wrote: > Am 03.10.2020 um 17:44 schrieb Bram Moolenaar: > > Therefore, I'm going to make && and || have a boolean result again. > > I think that is the easiest to understand, and what most languages do. > > +100 > > -- > Andy > -- -- You received this message from the "vim_dev" maillist. Do not top-post! Type your reply below the text you are replying to. For more information, visit http://www.vim.org/maillist.php --- You received this message because you are subscribed to the Google Groups "vim_dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to vim_dev+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/vim_dev/d82bdde2-4327-4907-a866-d57faf95ed2dn%40googlegroups.com.
Re: Vim9: rethinking conditions and boolean expressions
Am 03.10.2020 um 17:44 schrieb Bram Moolenaar: Therefore, I'm going to make && and || have a boolean result again. I think that is the easiest to understand, and what most languages do. +100 -- Andy -- -- You received this message from the "vim_dev" maillist. Do not top-post! Type your reply below the text you are replying to. For more information, visit http://www.vim.org/maillist.php --- You received this message because you are subscribed to the Google Groups "vim_dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to vim_dev+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/vim_dev/5F78D00C.3010704%40yahoo.de.
Vim9: rethinking conditions and boolean expressions
As a first approach I have used what TypeScript does. However, considering the feedback I have received, it's not very consistent and has a few surprising sides. One thing is that the "||" and "&&" operators do not result in a boolean true or false, but the argument value. This is nice for something like: var name = Getname() || 'unknown' When the result of Getname() is falsy (null or empty) then the result is "unknown". However, when the result should be a boolean, this does not work: var flag: bool = Getname() || false On top of that, the order matters, this works: var flag: bool = Getname() && true But this doesn't: var flag: bool = true && Getname() That is unexpected if you consider && to be a boolean expression. Therefore, I'm going to make && and || have a boolean result again. I think that is the easiest to understand, and what most languages do. For the first example, we can use a new operator which is specifically for testing an expression to be falsy and using a replacement: var name = Getname() ?? 'unknown' Let me know if you have comments. -- One difference between a man and a machine is that a machine is quiet when well oiled. /// Bram Moolenaar -- b...@moolenaar.net -- http://www.Moolenaar.net \\\ ///sponsor Vim, vote for features -- http://www.Vim.org/sponsor/ \\\ \\\ an exciting new programming language -- http://www.Zimbu.org/// \\\help me help AIDS victims -- http://ICCF-Holland.org/// -- -- You received this message from the "vim_dev" maillist. Do not top-post! Type your reply below the text you are replying to. For more information, visit http://www.vim.org/maillist.php --- You received this message because you are subscribed to the Google Groups "vim_dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to vim_dev+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/vim_dev/202010031544.093FiA401865731%40masaka.moolenaar.net.
