Foreach Range Statement

[Reiner Pope]

Bill Baxter wrote:
> Jarrett Billingsley wrote:
>> "Xinok" <xnknet at gmail.com> wrote in message 
>> news:f80qof$2n0l$1 at digitalmars.com...
>>
>>> foreach(i; 0..100)
>>
>> This is almost identical to the syntax in MiniD:
>>
>> for(i: 0 .. 100)
>>
>> It could be done with for or foreach; I just chose for because 
>> normally you use for loops to iterate over ranges of integers.
>>
>> You can also come up with a pretty simple short-term solution that'll 
>> be fairly efficient (though not as efficient as if the compiler were 
>> aware of this kind of loop intrinsically) by making a struct 'range' 
>> which has a static opCall to construct a range and an opApply to 
>> iterate over the values, so that it'd look like:
>>
>> foreach(i; range(100))
>>
>> Which isn't terrible at all. 
> 
> And it has the advantage of being more extensible.  And for allowing 
> ranges to be treated as first class entities that can be passed around 
> and manipulated.  But no, instead we get another one-trick pony.
> 
> --bb
That was my first thought, too.

In the "Array Slice Ranges" thread, several people mentioned first-class 
ranges:

http://www.digitalmars.com/pnews/read.php?server=news.digitalmars.com&group=digitalmars.D&artnum=43865
http://www.digitalmars.com/pnews/read.php?server=news.digitalmars.com&group=digitalmars.D&artnum=43904
http://www.digitalmars.com/pnews/read.php?server=news.digitalmars.com&group=digitalmars.D&artnum=43905
http://www.digitalmars.com/pnews/read.php?server=news.digitalmars.com&group=digitalmars.D&artnum=43954

Your implementation, Bill, seems to be just right, and gives you foreach 
over ranges for free.

What's wrong with adding that to the language, but templated and with 
nice syntax?

type name                                 literal
int..int  (range of int)                  1..5
int..double   (range of int to double)    1..5.0
int..int:int  (stepped range)             5..1:-1

(I'm not sure of the use of mixed-type ranges, but this seems the most 
intuitive syntax. Since most ranges are probably of one type, how about 
allowing a symbol to denote "same type again". Any of the following 
could mean int..int:   int..#,   int.._, int..$)

As several people have pointed out, this also fixes mixed 
indexing/slicing problems for multi-dimensional arrays.



   Reiner