Why is std.algorithm so complicated to use?

[Jacob Carlborg]

On 2012-07-10 15:28, Andrei Alexandrescu wrote:

> We can arrange things in the library that a custom message is issued, or
> in the compiler to do it once for all. At any rate whenever there's an
> error pointing somewhere in the library's code that's an insufficient
> template constraint that should be fixed.

I mean, is it possible to have the original code work?

auto bar = foo.chain("bar");

Or perhaps more appropriate:

auto bar = foo.append("bar");


> Well I made minimal changes. Besides I don't know what the intent is.

Have a look at this:

https://github.com/jacob-carlborg/dstep/blob/master/dstep/translator/Translator.d#L217

I was going to replace the foreach-loop in the above code with a call to 
"map". But "map" returns a range, not an array. Therefor the append at 
line 245 won't work. How would I do line 245 if "params" is a range 
returned by "map"?

It seems unnecessary to have to convert the range to an array before 
"join" is called on line 247.

> Indeed I agree there should be no error in library code. What I meant to
> say was, when I saw the code I thought "I bet this is an lvalue thing",
> and then when I saw lvalue in the error I was satisfied.

Jonathan has already reported these two bugs.

> I understand. So you need to use array() to convert the lazy map result
> into an eager array. I disagree this is unintuitive, if it were then
> very little of D would make sense are lazy, non-array ranges are
> everywhere.

Tell me what is the point of std.algorithm and ranges if I have to 
convert every single result of an algorithm to an array before I can use 
it with an other algorithm? I thought the whole idea was to avoid 
allocations between different usages of algorithms.

-- 
/Jacob Carlborg