• CJS (10/10) Dec 02 2013 In python a common performance tip for joining many strings
• Jacob Carlborg (10/20) Dec 02 2013 There's std.algorithm.joiner[1] and std.array.join[2]. I don't know if
• =?UTF-8?B?QWxpIMOHZWhyZWxp?= (17/37) Dec 03 2013 There is also the more general std.range.chain. It can join any type of

"CJS" <Prometheus85 hotmail.com> writes:

In python a common performance tip for joining many strings 
together is to use the join method. So, for example, instead of
"a" + "b" + "c"
use
''.join(["a","b","c"]).
The idea is to avoid creating temporary objects that are 
immediately thrown away. It's obviously overkill for such a small 
number of strings, though.

Is there any equivalent method/advice when concatenating many 
strings together in D?

Jacob Carlborg <doob me.com> writes:

On 2013-12-03 07:36, CJS wrote:
 In python a common performance tip for joining many strings together is
 to use the join method. So, for example, instead of
 "a" + "b" + "c"
 use
 ''.join(["a","b","c"]).
 The idea is to avoid creating temporary objects that are immediately
 thrown away. It's obviously overkill for such a small number of strings,
 though.

 Is there any equivalent method/advice when concatenating many strings
 together in D?

There's std.algorithm.joiner[1] and std.array.join[2]. I don't know if 
they're any more efficient than using "~". There's also 
std.array.Appender[3] if you want to do a lot of appending and want the 
most efficient way.

[1] http://dlang.org/phobos/std_algorithm.html#joiner



-- 
/Jacob Carlborg

=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:

On 12/02/2013 11:32 PM, Jacob Carlborg wrote:

 On 2013-12-03 07:36, CJS wrote:
 In python a common performance tip for joining many strings together is
 to use the join method. So, for example, instead of
 "a" + "b" + "c"
 use
 ''.join(["a","b","c"]).
 The idea is to avoid creating temporary objects that are immediately
 thrown away. It's obviously overkill for such a small number of strings,
 though.

 Is there any equivalent method/advice when concatenating many strings
 together in D?

 There's std.algorithm.joiner[1] and std.array.join[2]. I don't know if
 they're any more efficient than using "~".

They are more efficient in the sense that they are lazy.

 There's also
 std.array.Appender[3] if you want to do a lot of appending and want the
 most efficient way.

 [1] http://dlang.org/phobos/std_algorithm.html#joiner



There is also the more general std.range.chain. It can join any type of 
range as long as the element types are the same:

import std.stdio;
import std.range;
import std.algorithm;

void main()
{
     auto a_lazy_range_of_ints
         = chain(5.iota,
                 [ 10, 9, 20, 8 ].filter!(a => a < 10));

     // writeln consumes the range eagerly
     writeln(a_lazy_range_of_ints);

     // Prints [0, 1, 2, 3, 4, 9, 8]
}

Ali