Hello

A simple thing I stumbled across:

int main()
{
    import std.stdio;
    import std.range;

    int[] d;
    d ~= 10;
    d ~= 20;
    d.put(5);
    writeln(d);

    return 0;
}

Appenders work fine as output ranges, but arrays do not. The above code prints "20" (ie the 10 is removed). Is "put" not supposed to mean "append one element"?

Further, while the following compiles fine but runs really odd, the following does not compile:

int main()
{
    import std.stdio;
    import std.range;

    char[] c;
    c ~= 'a';
    c ~= 'b';
    c.put('c');
    writeln(c);

    return 0;
}

C:\dmd\src\phobos\std\range.d(9,9): Error: static assert  "Cannot put a char into a char[]." (Test)

I am puzzled by
1) Why I cannot put a char into a char[] (even though I can totally append them)
2) Why put removes elements from arrays

Hopefully somebody can help me clear my confusion about this (yes in the meantime I can just use Appenders, but you know, still wondering).

On 9/1/15 12:49 PM, default0 wrote:
> Hello
>
> A simple thing I stumbled across:
>
> int main()
> {
>      import std.stdio;
>      import std.range;
>
>      int[] d;
>      d ~= 10;
>      d ~= 20;
>      d.put(5);
>      writeln(d);
>
>      return 0;
> }
>
> Appenders work fine as output ranges, but arrays do not. The above code
> prints "20" (ie the 10 is removed). Is "put" not supposed to mean
> "append one element"?

put into an slice does not append, it fills in the front. This is because the "target" of a slice is the data it points at.

Think of it as a buffer that you want to fill:

int[20] buf;
int[] outputRange = buf[];
outputRange.put(10);
outputRange.put(20);

assert(buf[0..2] == [10,20]);

> Further, while the following compiles fine but runs really odd, the
> following does not compile:
>
> int main()
> {
>      import std.stdio;
>      import std.range;
>
>      char[] c;
>      c ~= 'a';
>      c ~= 'b';
>      c.put('c');
>      writeln(c);
>
>      return 0;
> }
>
> C:\dmd\src\phobos\std\range.d(9,9): Error: static assert  "Cannot put a
> char into a char[]." (Test)
>
> I am puzzled by
> 1) Why I cannot put a char into a char[] (even though I can totally
> append them)

That seems like a bug. put has specific code to deal with putting characters into character ranges. Please file https://issues.dlang.org/enter_bug.cgi

-Steve

On Tuesday, 1 September 2015 at 17:20:49 UTC, Steven Schveighoffer wrote:
> On 9/1/15 12:49 PM, default0 wrote:
>> Hello
>>
>> A simple thing I stumbled across:
>>
>> int main()
>> {
>>      import std.stdio;
>>      import std.range;
>>
>>      int[] d;
>>      d ~= 10;
>>      d ~= 20;
>>      d.put(5);
>>      writeln(d);
>>
>>      return 0;
>> }
>>
>> Appenders work fine as output ranges, but arrays do not. The above code
>> prints "20" (ie the 10 is removed). Is "put" not supposed to mean
>> "append one element"?
>
> put into an slice does not append, it fills in the front. This is because the "target" of a slice is the data it points at.
>
> Think of it as a buffer that you want to fill:
>
> int[20] buf;
> int[] outputRange = buf[];
> outputRange.put(10);
> outputRange.put(20);
>
> assert(buf[0..2] == [10,20]);
>
>> Further, while the following compiles fine but runs really odd, the
>> following does not compile:
>>
>> int main()
>> {
>>      import std.stdio;
>>      import std.range;
>>
>>      char[] c;
>>      c ~= 'a';
>>      c ~= 'b';
>>      c.put('c');
>>      writeln(c);
>>
>>      return 0;
>> }
>>
>> C:\dmd\src\phobos\std\range.d(9,9): Error: static assert  "Cannot put a
>> char into a char[]." (Test)
>>
>> I am puzzled by
>> 1) Why I cannot put a char into a char[] (even though I can totally
>> append them)
>
> That seems like a bug. put has specific code to deal with putting characters into character ranges. Please file https://issues.dlang.org/enter_bug.cgi
>
> -Steve


Thanks a lot for the clear explanation!
Issue has been created here: https://issues.dlang.org/show_bug.cgi?id=14998

Dne 1.9.2015 v 19:20 Steven Schveighoffer via Digitalmars-d-learn napsal(a):
> On 9/1/15 12:49 PM, default0 wrote:
>> Hello
>>
>> A simple thing I stumbled across:
>>
>> int main()
>> {
>>      import std.stdio;
>>      import std.range;
>>
>>      int[] d;
>>      d ~= 10;
>>      d ~= 20;
>>      d.put(5);
>>      writeln(d);
>>
>>      return 0;
>> }
>>
>> Appenders work fine as output ranges, but arrays do not. The above code
>> prints "20" (ie the 10 is removed). Is "put" not supposed to mean
>> "append one element"?
>
> put into an slice does not append, it fills in the front. This is because the "target" of a slice is the data it points at.
>
> Think of it as a buffer that you want to fill:
>
> int[20] buf;
> int[] outputRange = buf[];
> outputRange.put(10);
> outputRange.put(20);
>
> assert(buf[0..2] == [10,20]);
So it is something like this?:

int main()
{
    import std.stdio;
    import std.range;

    int[] d;
    d ~= [10];
    d ~= [20];
    d.front = 5;
    d.popFront();
    writeln(d);

    return 0;
}

On 9/1/15 3:13 PM, Daniel Kozak via Digitalmars-d-learn wrote:
>
>
> Dne 1.9.2015 v 19:20 Steven Schveighoffer via Digitalmars-d-learn
> napsal(a):
>> On 9/1/15 12:49 PM, default0 wrote:
>>> Hello
>>>
>>> A simple thing I stumbled across:
>>>
>>> int main()
>>> {
>>>      import std.stdio;
>>>      import std.range;
>>>
>>>      int[] d;
>>>      d ~= 10;
>>>      d ~= 20;
>>>      d.put(5);
>>>      writeln(d);
>>>
>>>      return 0;
>>> }
>>>
>>> Appenders work fine as output ranges, but arrays do not. The above code
>>> prints "20" (ie the 10 is removed). Is "put" not supposed to mean
>>> "append one element"?
>>
>> put into an slice does not append, it fills in the front. This is
>> because the "target" of a slice is the data it points at.
>>
>> Think of it as a buffer that you want to fill:
>>
>> int[20] buf;
>> int[] outputRange = buf[];
>> outputRange.put(10);
>> outputRange.put(20);
>>
>> assert(buf[0..2] == [10,20]);
> So it is something like this?:
>
> int main()
> {
>      import std.stdio;
>      import std.range;
>
>      int[] d;
>      d ~= [10];
>      d ~= [20];
>      d.front = 5;
>      d.popFront();
>      writeln(d);
>
>      return 0;
> }
>

I'm not following your code. What is the question?

-Steve

On 09/01/2015 02:16 PM, Steven Schveighoffer wrote:> On 9/1/15 3:13 PM, Daniel Kozak via Digitalmars-d-learn wrote:
>>
>>
>> Dne 1.9.2015 v 19:20 Steven Schveighoffer via Digitalmars-d-learn
>> napsal(a):
>>> On 9/1/15 12:49 PM, default0 wrote:
>>>> Hello
>>>>
>>>> A simple thing I stumbled across:
>>>>
>>>> int main()
>>>> {
>>>>      import std.stdio;
>>>>      import std.range;
>>>>
>>>>      int[] d;
>>>>      d ~= 10;
>>>>      d ~= 20;
>>>>      d.put(5);
>>>>      writeln(d);
>>>>
>>>>      return 0;
>>>> }
>>>>
>>>> Appenders work fine as output ranges, but arrays do not. The above code
>>>> prints "20" (ie the 10 is removed). Is "put" not supposed to mean
>>>> "append one element"?
>>>
>>> put into an slice does not append, it fills in the front. This is
>>> because the "target" of a slice is the data it points at.
>>>
>>> Think of it as a buffer that you want to fill:
>>>
>>> int[20] buf;
>>> int[] outputRange = buf[];
>>> outputRange.put(10);
>>> outputRange.put(20);
>>>
>>> assert(buf[0..2] == [10,20]);
>> So it is something like this?:
>>
>> int main()
>> {
>>      import std.stdio;
>>      import std.range;
>>
>>      int[] d;
>>      d ~= [10];
>>      d ~= [20];
>>      d.front = 5;
>>      d.popFront();
>>      writeln(d);
>>
>>      return 0;
>> }
>>
>
> I'm not following your code. What is the question?
>
> -Steve

I think Daniel is asking whether .put() on a slice is the equivalent of assigning to front() and then popFront(). The answer is yes.

http://dlang.org/phobos/std_range_primitives.html#.put

http://ddili.org/ders/d.en/ranges.html#ix_ranges.slice,%20as%20OutputRange

Ali