Creating InputRanges from strings, files etc.

[Alex]

On Thursday, 8 November 2018 at 16:15:25 UTC, Vinay Sajip wrote:
> On Thursday, 8 November 2018 at 14:38:37 UTC, Paul Backus wrote:
>> To pass these ranges around using the `InputRange` interface, 
>> use `inputRangeObject` to wrap them:
>>
>>     InputRange!ubyte r3 = inputRangeObject(r1);
>>     InputRange!(immutable(ubyte)) r4 = inputRangeObject(r2);
>
> I did a bit more digging, and it seems to work for strings but 
> not for files: The program
>
> import std.algorithm.iteration;
> import std.format;
> import std.range;
> import std.stdio;
> import std.string;
>
> void somefn(InputRange!(immutable(ubyte)) r) {
>     writeln(format!"%s"(r));
> }
>
> void main()
> {
>     auto a = "Hello, world!";
>     auto b = inputRangeObject(a.representation);
>     somefn(b);
>     auto c = stdin.byChunk(1024).joiner;
>     auto d = inputRangeObject(c);
>     //somefn(d);
> }
>
> compiles as given above, but if the somefn(d) line is 
> uncommented, I get an error:
>
> function onlineapp.somefn(InputRange!(immutable(ubyte)) r) is 
> not callable using argument types (InputRangeObject!(Result))
> onlineapp.d(18):        cannot pass argument d of type 
> std.range.interfaces.InputRangeObject!(Result) to parameter 
> InputRange!(immutable(ubyte)) r
>
> Do I need to do an explicit cast? If so, can someone tell me 
> the precise incantation? How come it doesn't figure out that 
> the underlying range is a ubyte range, or is it to do with 
> immutability, or something else altogether?

you could use a template for somefn definition:

´´´
void somefn(T)(T r) {
     writeln(format!"%s"(r));
}
´´´