Enhancements for the Range support

[WeihanLi]

Currently, when we use Range with an expression, we would get an error likes Operator '+' cannot be applied to operands of type 'int' and 'Range', CS0019

Could we make it more simple to use, wondering if it's possible to let the range operator .. priority lower than other operations so that we could use it without a brace

[kyoyama-kazusa]

Just add a brace: (i + 1)..

See docs:

https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/operators/#operator-precedence

Picture:

[WeihanLi]

Thanks, I know this, I'm wondering if it's possible to let it work without the brace

[kyoyama-kazusa]

@WeihanLi Hello.

(i + 1).. and i + 1.. are two different expressions. For the reference of the operator precedence, we know that i + 1.. means a variable i adds a range expression 1.., which is incorrect. We know that an integer cannot add to a range expression because of not being defined.

Actually, I prefer the brace-styled syntax rather than i + 1.. because i + 1.. is not clear enough. Generally, a range expression can omit start index or end index, or both, which means the expression will be like:

• 1..
• ..^2
• ..

Which makes the range syntax be more like a unary expression. A unary expression always has a higher priority than the binary one, for example, ++x has a higher priority than x + 1. If we assign a range expression with a lower precedence, the rule will be broken.

For me, if without a brace, the readability will be slow down because I may often misread the expression, to get an incorrect expression i + (1..) instead of (i + 1).. because IDE always inserts a whitespace into the place between plus sign + and literal one 1.

[svick]

Could we make it more simple to use

What is the suggested solution? Since changing the precedence would be a breaking change, I don't think it's likely that code like p[i+1..] will ever compile. Would a quick fix that adds the parentheses for you be enough?

[333fred]

The precedence of .. was very intentionally chosen to bind tighter than +. .. is usually written without spaces, and + is usually written with spaces. We feel that it would be confusing to the reader if the thing with spaces binds tighter than the thing without them, as the rest of C# doesn't work this way.