Re: how does range.put work
Daniel Keep wrote:
No; read the code. Before the put, a and b are pointing to the same
span of memory. a.put(5) puts the value 5 into the front (first
element) of the array, then advances the array.
However, put can't "see" b, so it doesn't get updated along with a. The
end result is that b = [5,2,3] and a = b[1..3] = [2,3].
Why do it like this? Here's an example:
void putNumbers(Range)(Range r)
{
int i = 0;
while( !r.empty )
{
r.put(i);
++i;
}
}
void main()
{
int[10] ten_numbers;
putNumbers(ten_numbers);
assert( ten_numbers = [0,1,2,3,4,5,6,7,8,9] );
}
I see.
Your example should be in the documentation in my opinion, rather
then the meaningless one that's there now. Something like this
perhaps:
void putNumbers(Range, T)(Range r, T start, T incr) {
T i = start;
while( !r.empty )
{
r.put(i);
i += incr;
}
}
void main() {
int[10] ten_ints;
putNumbers!(int[])(ten_ints, 4, 2);
assert( ten_ints == [4,6,8,10,12,14,16,18,20,22] );
}
Jos
Re: how does range.put work
Jos van Uden wrote:
> Oliver wrote:
>>> The source code for the standard library comes with the compiler.
>>> If you look in std\array.d, you find this around line 279 (reflowed for
>>> readability):
void put(T, E)(ref T[] a, E e) {
assert(a.length);
a[0] = e; a = a[1 .. $];
}
>
> Would anybody care to explain what this is used for? I find
> the example in array.d rather unhelpful.
>
> Example:
>
> void main()
> {
> int[] a = [ 1, 2, 3 ];
> int[] b = a;
> a.put(5);
> assert(a == [ 2, 3 ]);
> assert(b == [ 5, 2, 3 ]);
> }
>
> You're putting an element in a, but then the first element is moved out
> of a and the new one shows up in b? Weird. I guess I don't understand
> what a range is.
>
> Jos
No; read the code. Before the put, a and b are pointing to the same
span of memory. a.put(5) puts the value 5 into the front (first
element) of the array, then advances the array.
However, put can't "see" b, so it doesn't get updated along with a. The
end result is that b = [5,2,3] and a = b[1..3] = [2,3].
Why do it like this? Here's an example:
void putNumbers(Range)(Range r)
{
int i = 0;
while( !r.empty )
{
r.put(i);
++i;
}
}
void main()
{
int[10] ten_numbers;
putNumbers(ten_numbers);
assert( ten_numbers = [0,1,2,3,4,5,6,7,8,9] );
}
Note that putNumbers will work with any type that supports the range
API, not just arrays.
Re: how does range.put work
Oliver wrote:
The source code for the standard library comes with the compiler.
If you look in std\array.d, you find this around line 279 (reflowed for
readability):
void put(T, E)(ref T[] a, E e) {
assert(a.length);
a[0] = e; a = a[1 .. $];
}
Would anybody care to explain what this is used for? I find
the example in array.d rather unhelpful.
Example:
void main()
{
int[] a = [ 1, 2, 3 ];
int[] b = a;
a.put(5);
assert(a == [ 2, 3 ]);
assert(b == [ 5, 2, 3 ]);
}
You're putting an element in a, but then the first element is moved out
of a and the new one shows up in b? Weird. I guess I don't understand
what a range is.
Jos
Re: how does range.put work
Good point ! Use the [S/F]o[u]rce !
Thx, Oliver
> O.K. wrote:
> > Hello,
> > could someone plz clearify what the exact semantics of "put"
> > are ?
> > Put works with an appender, but gives me a runtime exception
> > when using an array.
> >
> > Best regards,
> > Oliver
> The source code for the standard library comes with the compiler.
> If you look in std\array.d, you find this around line 279 (reflowed for
> readability):
> > void put(T, E)(ref T[] a, E e) {
> > assert(a.length);
> > a[0] = e; a = a[1 .. $];
> > }
Re: how does range.put work
O.K. wrote:
> Hello,
> could someone plz clearify what the exact semantics of "put"
> are ?
> Put works with an appender, but gives me a runtime exception
> when using an array.
>
> Best regards,
> Oliver
The source code for the standard library comes with the compiler.
If you look in std\array.d, you find this around line 279 (reflowed for
readability):
> void put(T, E)(ref T[] a, E e) {
> assert(a.length);
> a[0] = e; a = a[1 .. $];
> }
how does range.put work
Hello, could someone plz clearify what the exact semantics of "put" are ? Put works with an appender, but gives me a runtime exception when using an array. Best regards, Oliver
