- Created: 2016-08-24 by arBmind
- Updated: 2018-06-03 by arBmind
This RFC proposes a way to handle epxression separation and continuations without the use of separator signs like semicolons.
In order to get a very fluent language we should not require semicolons. Semicolons are one of the hardest things to learn in a programming language.
Removing the requirement to place semicolons between all statements reduces a huge error potential for programmers.
This paper proposes the use of indentation for line continuations. This is a visual approach that is also used by Python.
Two lines with the same indentation are treated as two separate expressions.
line1
line2
If the second line is indented more, the expression started in the first line is continued in the second line.
line1
line2
Unlike Python we do not want to impose our own preference to every developer.
Both styles are allowed. But mixing them in one file is an error.
- Once the compiler has seen tabs for indentation, the use of spaces for indentations is an error.
- Vice versa, once Spaces were used for indentations, the use of tabs for indentations is an error.
Nesting continuations deeper should be allowed. This will help to group arguments in complex calls.
This should be valid.
line1
continue1
continue1a
continue2
All lines above are parsed as if it was one line, with whitespaces where the line breaks are.
It should be illegal to jump above it first continuation line.
line1
continue1
more # <= error
Visually this pattern is reserved for blocks.
The error should propose to start a block or indent the line correctly.
Internally the more starts a block and is added to the line continuation.
Later errors in parsing either of these are ignored.
As every developer should indent these statements any way, so they become readable. I do not the a large issue here.
IDEs have a hard time to help you do the right thing. They basically do not know if a line should be continued or seperated.
A good IDE might use the same rules as automatic semicolon insertions and try to help the programmer to get it right. The big benefit here is that the solution is visible and errors can easily be fixed.
As stated in the motivation, we want to avoid the noise of adding semicolons or any other delimiter.
We could define rules like Javascript and Ruby that insert semicolons automatically.
Even though this works fine most of the time. When it fails to do the right thing nobody seems to remember all the rules and edge cases.
This would basically be the inverse rule to a semicolon. It is also visually not pleasing and kind of hard to maintain.
None so far.