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digitalmars.D.learn - Range to array

reply "Namespace" <rswhite4 googlemail.com> writes:
It is terrible to use a function of std.range if you are not 
using "auto" as type all the time.
Why isn't there a convert function for the original type?
I know "array(Range)" of std.array is what i want, but why do i 
have to import two  modules to use one?
Wouldn't it be better if std.range imports std.array implicit?
Otherwise (IMO) std.range needs some convert functions like

[code]
T[] Range(alias func, T)(T[] array) {
	return func(array).array();
}

T[] Range(alias func, T, U)(T[] array, U a) {
	return func(array, a).array();
}

T[] Range(alias func, T, U)(T a, U b) if (!isArray!(T)) {
	return func(a, b).array();
}
[/code]

or, if you prefer, in compressed (but without the type safety):
[code]
auto Range(alias func, Args...)(Args args) {
	return func(args).array();
}
[/code]

I think something like that is missing in std.range.
Jun 29 2012
next sibling parent Jonathan M Davis <jmdavisProg gmx.com> writes:
On Saturday, June 30, 2012 01:43:44 Namespace wrote:
 It is terrible to use a function of std.range if you are not
 using "auto" as type all the time.
 Why isn't there a convert function for the original type?
 I know "array(Range)" of std.array is what i want, but why do i
 have to import two  modules to use one?
 Wouldn't it be better if std.range imports std.array implicit?
 Otherwise (IMO) std.range needs some convert functions like

std.range already publicly import std.array. Not to mention, if you're using ranges heavily, it's not all that uncommon to not actually need std.array.array very often. In general, if you're constantly converting ranges to arrays, then I'd argue that you're doing something wrong. There are definitely times when you need to convert a range to an array, but in general, you can just pass the result of one range-based function to another and operate on the data just fine without needing to convert to arrays at all. Worst case, you convert once you're done with all of various operations that you need to do on the data. But if you're passing arrays around rather than ranges, unless you actually need arrays for some reason, you should really consider passing ranges around like Phobos does. You're code's not going to be terribly efficient if you're constantly converting the results of range-based functions into arrays, since that means allocating more memory for the same data every time that you do that. - Jonathan M Davis
Jun 29 2012
prev sibling next sibling parent "Namespace" <rswhite4 googlemail.com> writes:
 std.range already publicly import std.array.

Oh, good to known.
 Not to mention, if you're using ranges heavily, it's not all 
 that uncommon to
 not actually need std.array.array very often. In general, if 
 you're constantly
 converting ranges to arrays, then I'd argue that you're doing 
 something wrong.
 There are definitely times when you need to convert a range to 
 an array, but in
 general, you can just pass the result of one range-based 
 function to another
 and operate on the data just fine without needing to convert to 
 arrays at all.
 Worst case, you convert once you're done with all of various 
 operations that
 you need to do on the data. But if you're passing arrays around 
 rather than
 ranges, unless you actually need arrays for some reason, you 
 should really
 consider passing ranges around like Phobos does. You're code's 
 not going to be
 terribly efficient if you're constantly converting the results 
 of range-based
 functions into arrays, since that means allocating more memory 
 for the same
 data every time that you do that.

 - Jonathan M Davis

But a Range don't match any function that accept arrays. Or should i prefer to use Ranges instead of arrays?
Jun 30 2012
prev sibling next sibling parent Jonathan M Davis <jmdavisProg gmx.com> writes:
On Saturday, June 30, 2012 11:06:06 Namespace wrote:
 But a Range don't match any function that accept arrays. Or
 should i prefer to use Ranges instead of arrays?

In general, functions should take ranges, not arrays. They're far more flexible that way. Requiring an array is generally overly restrictive. There are, of course, cases where you really do need to operate on an array or string, or where it's pointless to take anything else (e.g. if you're going to pass a zero-terminated string to a C function, then there's no point in taking a range of dchar instead of a string), but in general, functions should operate on ranges, not arrays. Just look at Phobos. For the most part, it operates on ranges, not arrays. The only real exception in general is that if a function needs to operate on characters (rather than being generic with its type), then it's likely to be templatized on string type rather than on range type, but due to the fact that strings are variably length encoded, operating on them as ranges tends to be inefficent (which is why range-based functions frequently have overloads specifically for strings). So, ranges which wrap strings tend to be converted to strings far more often than other arrays do. But it's arguably the case that more of Phobos' functions which operate on strings should take ranges of dchar instead. - Jonathan M Davis
Jun 30 2012
prev sibling parent "bearophile" <bearophileHUGS lycos.com> writes:
Namespace:

 Or should i prefer to use Ranges instead of arrays?

There is no short answer to this question. Arrays and lazy ranges have different qualities, so they are better for different situations. Arrays use more memory, but in some situations they are faster. Lazy ranges can be a little more complex to use. Often I use ranges where I can, and arrays in the other cases, or where I have to modify the array items many times. Bye, bearophile
Jun 30 2012