This code breaks with the following error:
void main()
{
	import std.range;
  	int[] vals = [];
	vals.put(3);
}
/src/phobos/std/range/primitives.d(2328): Attempting to fetch the front of an empty array of int

The following code has no error:
void main()
{
	import std.range;
  	int[] vals = [1];
	vals.put(3);
}

Why is range.put() not allowed for empty arrays?

On 6/17/18 7:07 AM, Vijay Nayar wrote:
> This code breaks with the following error:
> void main()
> {
>      import std.range;
>        int[] vals = [];
>      vals.put(3);
> }
> /src/phobos/std/range/primitives.d(2328): Attempting to fetch the front of an empty array of int
> 
> The following code has no error:
> void main()
> {
>      import std.range;
>        int[] vals = [1];
>      vals.put(3);
> }
> 
> Why is range.put() not allowed for empty arrays?
> 
> 

range.put fills an existing array like a buffer, it does not append (as I'm guessing you are expecting). Use std.array.Appender to get append behavior.

BTW, use put(vals, 3) instead of vals.put(3), as you may bypass the features of put.

-Steve

On Sunday, 17 June 2018 at 12:23:55 UTC, Steven Schveighoffer wrote:
> On 6/17/18 7:07 AM, Vijay Nayar wrote:
>> This code breaks with the following error:
>> void main()
>> {
>>      import std.range;
>>        int[] vals = [];
>>      vals.put(3);
>> }
>> /src/phobos/std/range/primitives.d(2328): Attempting to fetch the front of an empty array of int
>> 
>> The following code has no error:
>> void main()
>> {
>>      import std.range;
>>        int[] vals = [1];
>>      vals.put(3);
>> }
>> 
>> Why is range.put() not allowed for empty arrays?
>> 
>> 
>
> range.put fills an existing array like a buffer, it does not append (as I'm guessing you are expecting). Use std.array.Appender to get append behavior.

Or simply ~= if you want to use built-in arrays (works with Appender too FWIW).