A lexical change (a breaking change, but trivial to fix)

[Mehrdad]

On Saturday, 7 July 2012 at 22:00:43 UTC, H. S. Teoh wrote:
> On Sat, Jul 07, 2012 at 11:39:59PM +0200, Mehrdad wrote:
>> This might sound silly, but how about if D stopped allowing   
>> 0..2
>> as a range, and instead just said "invalid floating-point 
>> number"?
> [...]
>
> I like writing 0..2 as a range. It's especially nice in array 
> slice notation, where you _want_ to have it as concise as 
> possible.

Hmm... true..

> OTOH, having implemented a D lexer before (just for practice, 
> not production quality), I do see how ambiguities with 
> floating-point numbers can cause a lot of code convolutions.

Yeah that's exactly what happened to me lol.
(Mainly the problem I ran into was that I was REALLY trying to 
avoid extra lookaheads if possible, since I was sticking to the 
range interface of front/popFront, and trying not to consume more 
than I can handle... and this was the edge case that broke it.)

> But I'm gonna have to say no to this one; *I* think a better 
> solution would be to prohibit things like 0. or 1. in a float 
> literal. Either follow it with a digit, or don't write the dot. 
> This will also save us a lot of pain in the UFCS department, 
> where 4.sqrt is currently a pain to lex. Once this is done, 
> 0..2 is no longer ambiguous, and any respectable DFA lexer 
> should be able to handle it with ease.

Good idea, I like it too. How about just disallowing trailing 
decimal points then?