Derek Parnell wrote:
Because
1. case X..Y:
looks like
2. foreach(e; X..Y)
3. array[X..Y]
4. case X:..caseY:
yet the X..Y has a VERY DIFFERENT meaning. (1) is inclusive of Y, and
(2) and (3) are exclusive of Y, and (4) is inclusive of Y ... oh, hang
on...
Sorry, but I'm just not getting the "VERY DIFFERENT" part yet. Right now, D
has ".." meaning exclude-end value (2. and 3.) AND it also has ".." meaning
include-end value (4.), depending on context.
I think here's the point where our thinking diverges. You say ".." has a
meaning. No. It does not have any meaning. It's punctuation. Same way,
"*", "&", ":", ",", etc. have no meaning in D all alone. They are
tokens. They acquire a meaning by partaking in grammatical constructs.
What does have arguably a meaning is "expression1 .. expression2". (Even
that could be debatable because it's not a standalone expression). But
anyway, the meaning that "expression1 .. expression2" acquires in array
slices and foreach statements is uniform.
Now we have the different construct "case expression1: .. case
expression2:" That is evidently not "expression1 .. expression2", does
not include it as a part, and shares essentially nothing except the ".."
with it. That's my point.
Ok, I admit that there is one subtle difference. Examples 2 and 3 are of
the form
IntExpression .. IntExpression
and example 4 is
CaseLabelInt .. CaseLabelInt
but seriously, people are not going to notice that. We see double-dot and
think "range".
You should see "expression1 .. expression2" and think "range". There's
very few tokens that make one think of only one thing when seeing them.
One of them is "%" - makes one think of modulus, another is "^" meaning
xor, another is "$" - array size... but that's about it.
I know that this is not ever going to be changed so I'm not arguing that it
should.
(One of the most frequent bugs I have in my D programs is that I forget
that X..Y excludes Y because it's not natural to me to see text that looks
like "the range X to Y" but means "the range X to Y-1".)
It seems that D would benefit from having a standard syntax format for
expressing various range sets;
a. Include begin Include end, i.e. []
b. Include begin Exclude end, i.e. [)
c. Exclude begin Include end, i.e. (]
d. Exclude begin Exclude end, i.e. ()
I'm afraid this would majorly mess with pairing of parens.
Andrei
