Things like this should "just work"..

File input ...

auto range = input.byLine();
while(!range.empty)
{
  range.popFront();
  foreach (i, line; range.take(4))  //Error: cannot infer argument types
  {
    ..etc..
  }
  range.popFront();
}

Tried adding 'int' and 'char[]' or 'auto' .. no dice.

Can someone explain why this fails, and if this is a permanent or temporary limitation of D/MD.

R

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On Tuesday, 11 February 2014 at 10:10:27 UTC, Regan Heath wrote:
> Things like this should "just work"..
>
> File input ...
>
> auto range = input.byLine();
> while(!range.empty)
> {
>   range.popFront();
>   foreach (i, line; range.take(4))  //Error: cannot infer argument types
>   {
>     ..etc..
>   }
>   range.popFront();
> }
>
> Tried adding 'int' and 'char[]' or 'auto' .. no dice.
>
> Can someone explain why this fails, and if this is a permanent or temporary limitation of D/MD.
>
> R

See this pull request[1] and the linked enhancement report.

Also note that calling `r.popFront()` without checking `r.empty` is a program error (so it's recommended to at least put in an assert).

[1] https://github.com/D-Programming-Language/phobos/pull/1866

On Tue, 11 Feb 2014 10:10:27 -0000, Regan Heath <regan@netmail.co.nz> wrote:

> Things like this should "just work"..
>
> File input ...
>
> auto range = input.byLine();
> while(!range.empty)
> {
>    range.popFront();
>    foreach (i, line; range.take(4))  //Error: cannot infer argument types
>    {
>      ..etc..
>    }
>    range.popFront();
> }
>
> Tried adding 'int' and 'char[]' or 'auto' .. no dice.
>
> Can someone explain why this fails, and if this is a permanent or temporary limitation of D/MD.

Further, the naive solution of adding .array gets you in all sorts of trouble :p  (The whole byLine buffer re-use issue).

This should be simple and easy, dare I say it trivial.. or am I just being dense here.

R

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> Further, the naive solution of adding .array gets you in all sorts of trouble :p  (The whole byLine buffer re-use issue).
>
> This should be simple and easy, dare I say it trivial.. or am I just being dense here.
>
> R

The second naive solution would be to use readText and splitLines.

On Tuesday, 11 February 2014 at 10:10:27 UTC, Regan Heath wrote:
> Things like this should "just work"..
>
> File input ...
>
> auto range = input.byLine();
> while(!range.empty)
> {
>   range.popFront();
>   foreach (i, line; range.take(4))  //Error: cannot infer argument types
>   {
>     ..etc..
>   }
>   range.popFront();
> }
>
> Tried adding 'int' and 'char[]' or 'auto' .. no dice.
>
> Can someone explain why this fails, and if this is a permanent or temporary limitation of D/MD.
>
> R
Is foreach(i, val; aggregate) even defined if aggr is not an array or associated array? It is not in the docs: http://dlang.org/statement#ForeachStatement

On Tue, 11 Feb 2014 10:52:39 -0000, Tobias Pankrath <tobias@pankrath.net> wrote:

>> Further, the naive solution of adding .array gets you in all sorts of trouble :p  (The whole byLine buffer re-use issue).
>>
>> This should be simple and easy, dare I say it trivial.. or am I just being dense here.
>>
>> R
>
> The second naive solution would be to use readText and splitLines.

The file is huge in my case :)

R

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On Tue, 11 Feb 2014 10:58:17 -0000, Tobias Pankrath <tobias@pankrath.net> wrote:

> On Tuesday, 11 February 2014 at 10:10:27 UTC, Regan Heath wrote:
>> Things like this should "just work"..
>>
>> File input ...
>>
>> auto range = input.byLine();
>> while(!range.empty)
>> {
>>   range.popFront();
>>   foreach (i, line; range.take(4))  //Error: cannot infer argument types
>>   {
>>     ..etc..
>>   }
>>   range.popFront();
>> }
>>
>> Tried adding 'int' and 'char[]' or 'auto' .. no dice.
>>
>> Can someone explain why this fails, and if this is a permanent or temporary limitation of D/MD.
>>
>> R
> Is foreach(i, val; aggregate) even defined if aggr is not an array or associated array? It is not in the docs: http://dlang.org/statement#ForeachStatement

import std.stdio;

struct S1 {
   private int[] elements = [9,8,7];
   int opApply (int delegate (ref uint, ref int) block) {
       foreach (uint i, int n ; this.elements)
           block(i, n);
       return 0;
   }
}

void main()
{
	S1 range;	
	foreach(uint i, int x; range)
	{
	  writefln("%d is %d", i, x);
	}
}

R

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On Tuesday, 11 February 2014 at 13:00:19 UTC, Regan Heath wrote:
> import std.stdio;
>
> struct S1 {
>    private int[] elements = [9,8,7];
>    int opApply (int delegate (ref uint, ref int) block) {
>        foreach (uint i, int n ; this.elements)
>            block(i, n);
>        return 0;
>    }
> }
>
> void main()
> {
> 	S1 range;	
> 	foreach(uint i, int x; range)
> 	{
> 	  writefln("%d is %d", i, x);
> 	}
> }
>
> R

byLine does not use opApply
https://github.com/D-Programming-Language/phobos/blob/master/std/stdio.d#L1389

On Tuesday, 11 February 2014 at 10:10:27 UTC, Regan Heath wrote:
> Things like this should "just work"..
>
> File input ...
>
> auto range = input.byLine();
> while(!range.empty)
> {
>   range.popFront();
>   foreach (i, line; range.take(4))  //Error: cannot infer argument types
>   {
>     ..etc..
>   }
>   range.popFront();
> }
>
> Tried adding 'int' and 'char[]' or 'auto' .. no dice.
>
> Can someone explain why this fails, and if this is a permanent or temporary limitation of D/MD.
>
> R

foreach (i, line; iota(size_t.max).zip(range.take(4)))
{

}

On 02/11/2014 06:25 AM, Rene Zwanenburg wrote:
> On Tuesday, 11 February 2014 at 10:10:27 UTC, Regan Heath wrote:

>>   foreach (i, line; range.take(4))  //Error: cannot infer argument types
>>   {
>>     ..etc..
>>   }

> foreach (i, line; iota(size_t.max).zip(range.take(4)))
> {
>
> }

There is also the following, relying on tuples' automatic expansion in foreach:

    foreach (i, element; zip(sequence!"n", range.take(4))) {
        // ...
    }

Ali