Output range and writeln style functions

[Ali Çehreli via Digitalmars-d-learn]

On 01/23/2017 12:48 PM, Jon Degenhardt wrote:
> On Monday, 23 January 2017 at 08:03:14 UTC, Ali Çehreli wrote:
>> On 01/22/2017 01:54 PM, Jon Degenhardt wrote:
>>> I've been increasingly using output ranges in my code (the "component
>>> programming" model described in several articles on the D site). It
>>> works very well, except that it would often be more convenient to use
>>> writeln style functions rather than 'put'. Especially when you start by
>>> drafting a sketch of code using writeln functions, then convert it an
>>> output range.
>>>
>>> Seems an obvious thing, I'm wondering if I missed something. Are there
>>> ways to use writeln style functions with output ranges?
>>>
>>> --Jon
>>
>> I don't think I understand the question. :)
>>
>> If you need a variadic put(), then I've come up with the following
>> mildly tested AllAppender. Just as a reminder, I've also used
>> std.range.tee that allows tapping into the stream to see what's flying
>> through:
>>
>> [snip]
>>
>> Ali
>
> So I guess the is answer is "no" :)
>
> It's mainly about consistency of the output primitives. Includes
> variadic args, formatting, and names of the primitives. I keep finding
> myself starting with something like:
>
>     void writeLuckyNumber(string name, int luckyNumber)
>    {
>        writefln("Hello %s, your lucky number is %d", name, luckyNumber);
>    }
>
> and then re-factoring it as:
>
>    void writeLuckyNumber(OutputRange)
>        (OutputRange outputStream, string name, int luckyNumber)
>        if (isOutputRange!(OutputRange, char))
>    {
>        import std.format;
>        outputStream.put(
>            format("Hello %s, your lucky number is %d\n", name,
> luckyNumber));
>    }
>
> Not bad, but the actual output statements are a bit harder to read,
> especially if people reading your code are not familiar with output
> ranges. So, what I'm really wondering is if there is built-in way to get
> closer to:
>
>       outputStream.writefln(...);
>
>  that I've overlooked.
>
>
> --Jon

If it's about formatted output then perhaps formattedWrite?

   https://dlang.org/phobos/std_format.html#.formattedWrite

The same function is used with stdout and an Appender:

import std.stdio;
import std.range;

void writeLuckyNumber(OutputRange)
(OutputRange outputStream, string name, int luckyNumber)
if (isOutputRange!(OutputRange, char))
{
     import std.format : formattedWrite;
     formattedWrite(outputStream, "Hello %s, your lucky number is %d\n", 
name, luckyNumber);
}

void main() {
     writeLuckyNumber(stdout.lockingTextWriter, "Jon", 42);

     auto app = appender!string();
     writeLuckyNumber(app, "Jon", 42);

     writeln(app.data);
}

Ali