• bearophile (23/23) Feb 16 2014 In the last days of beta3 D+Phobos is getting better in small but
• Bienlein (9/23) Feb 19 2014 There is the nice old Smalltalk-80 inject:into: method in the
• bearophile (5/13) Feb 19 2014 In D there's std.algorithm.reduce.
• Philippe Sigaud (7/11) Feb 19 2014 Oh, but D has `reduce`, for years now. It was maybe one of the very
• Bienlein (7/10) Feb 19 2014 I see. Unhappily, I don't have a D compiler handy. Would this
• Dicebot (2/7) Feb 19 2014 This works right now: immutable s = ["red", "blue"].join("");
• Philippe Sigaud (3/6) Feb 19 2014 It won't work, since binary + is not defined for strings. I don't
• Bienlein (4/16) Feb 19 2014 Then how can you add a sum method to a parameterized type if it
• Dicebot (3/5) Feb 19 2014 As far as I understand it will work on anything that has binary
• bearophile (6/9) Feb 19 2014 This could work, but join() is (or should be) asymptotically more
• Suliman (20/20) Feb 19 2014 Hm, I got next error on this code
• Dicebot (12/20) Feb 19 2014 This works:
• Timon Gehr (2/4) Feb 19 2014 No, a custom separator is not mandatory.
• Dicebot (3/10) Feb 19 2014 Ah, my bad, was expecting a default parameter, not an extra
• Gary Willoughby (2/25) Feb 19 2014 What is q{a + b} ?
• Dicebot (3/4) Feb 19 2014 http://dlang.org/lex.html#TokenString

"bearophile" <bearophileHUGS lycos.com> writes:

In the last days of beta3 D+Phobos is getting better in small but 
significant ways:

immutable s = ["red", "blue"];
auto js = s.join;

This is very handy because you can join arrays from constant 
function arguments, or the result of a map that yields const 
items, etc.

-----------------------

And I am finding the optional column number in error messages 
very handy, my editor/IDE often jumps at the right column, saving 
me tiny amounts of time that adds up making the debugging nicer. 
The experience is just better than before.

-----------------------

auto r = [10, 20, 30].sum;

This has replaced me tens of usages of:
alias sum = reduce!q{a + b};
Or:
alias sum = curry!(reduce!q{a + b}, 0);


But I have found problems because currently sum(int[]) returns a 
long, see the discussion so far:
https://d.puremagic.com/issues/show_bug.cgi?id=12169

Bye,
bearophile

"Bienlein" <jeti789 web.de> writes:

On Sunday, 16 February 2014 at 13:22:09 UTC, bearophile wrote:
 In the last days of beta3 D+Phobos is getting better in small 
 but significant ways:

 immutable s = ["red", "blue"];
 auto js = s.join;

 This is very handy because you can join arrays from constant 
 function arguments, or the result of a map that yields const 
 items, etc.

 -----------------------

 And I am finding the optional column number in error messages 
 very handy, my editor/IDE often jumps at the right column, 
 saving me tiny amounts of time that adds up making the 
 debugging nicer. The experience is just better than before.

 -----------------------

 auto r = [10, 20, 30].sum;

There is the nice old Smalltalk-80 inject:into: method in the 
Collection class:

| list sum |
list := OrderedCollection new add: 1; add: 2; add: 3; yourself.
sum := list inject: 0 into: [ :a :b | a + b ].
Transcript cr; show: sum.  "prints 6"

A little more general ;-). The Scala guys have also cloned it 
where it is called foldLeft.

"bearophile" <bearophileHUGS lycos.com> writes:

Bienlein:

 There is the nice old Smalltalk-80 inject:into: method in the 
 Collection class:

 | list sum |
 list := OrderedCollection new add: 1; add: 2; add: 3; yourself.
 sum := list inject: 0 into: [ :a :b | a + b ].
 Transcript cr; show: sum.  "prints 6"

 A little more general ;-). The Scala guys have also cloned it 
 where it is called foldLeft.

In D there's std.algorithm.reduce.
I think Scala guys have copied something older than Smalltalk.

Bye,
bearophile

Philippe Sigaud <philippe.sigaud gmail.com> writes:

On Wed, Feb 19, 2014 at 1:29 PM, Bienlein <jeti789 web.de> wrote:
 There is the nice old Smalltalk-80 inject:into: method in the Collection
 class:

 A little more general ;-). The Scala guys have also cloned it where it is
 called foldLeft.

Oh, but D has `reduce`, for years now. It was maybe one of the very
first range algorithms to be put into Phobos, with map and filter. So
we have generality already :-)

What bearophile wanted was, on the contrary, to have a
specialized-for-summing function, if only to make the intended
behavior more clear.

"Bienlein" <jeti789 web.de> writes:

On Wednesday, 19 February 2014 at 12:43:10 UTC, Philippe Sigaud 
wrote:
 What bearophile wanted was, on the contrary, to have a
 specialized-for-summing function, if only to make the intended
 behavior more clear.

I see. Unhappily, I don't have a D compiler handy. Would this 
compile:

immutable s = ["red", "blue"].sum

If not, it would be interesting to understand how that works :-)

-- Bienlein

"Dicebot" <public dicebot.lv> writes:

On Wednesday, 19 February 2014 at 13:18:15 UTC, Bienlein wrote:
 I see. Unhappily, I don't have a D compiler handy. Would this 
 compile:

 immutable s = ["red", "blue"].sum

 If not, it would be interesting to understand how that works :-)

 -- Bienlein

This works right now: immutable s = ["red", "blue"].join("");

Philippe Sigaud <philippe.sigaud gmail.com> writes:

On Wed, Feb 19, 2014 at 2:18 PM, Bienlein <jeti789 web.de> wrote:
 I see. Unhappily, I don't have a D compiler handy. Would this compile:

 immutable s = ["red", "blue"].sum

 If not, it would be interesting to understand how that works :-)

It won't work, since binary + is not defined for strings. I don't
understand what you want, here.

"Bienlein" <jeti789 web.de> writes:

On Wednesday, 19 February 2014 at 13:53:17 UTC, Philippe Sigaud 
wrote:
 On Wed, Feb 19, 2014 at 2:18 PM, Bienlein <jeti789 web.de> 
 wrote:
 I see. Unhappily, I don't have a D compiler handy. Would this 
 compile:

 immutable s = ["red", "blue"].sum

 If not, it would be interesting to understand how that works 
 :-)

 It won't work, since binary + is not defined for strings. I 
 don't
 understand what you want, here.

Then how can you add a sum method to a parameterized type if it 
only works for numbers?

"Dicebot" <public dicebot.lv> writes:

On Wednesday, 19 February 2014 at 14:02:38 UTC, Bienlein wrote:
 Then how can you add a sum method to a parameterized type if it 
 only works for numbers?

As far as I understand it will work on anything that has binary 
operator "+" defined.

"bearophile" <bearophileHUGS lycos.com> writes:

Bienlein:

 Would this compile:

 immutable s = ["red", "blue"].sum

 If not, it would be interesting to understand how that works :-)

This could work, but join() is (or should be) asymptotically more 
efficient:

reduce!q{a ~ b}("", ["red", "blue"])

Bye,
bearophile

"Suliman" <evermind live.ru> writes:

Hm, I got next error on this code

import std.stdio;
import std.array;

void main()
{
immutable s = ["red", "blue"];
auto js = s.join;
}


D:\Project\2014\App1\main.d(7): Error: template std.array.join 
cannot deduce function from argument types 
!()(immutable(char[][])), candidates are:
C:\D\dmd2\windows\bin\..\..\src\phobos\std\array.d(1526):        
std.array.join(RoR, R)(RoR ror, R sep) if (isInputRange!RoR && 
isInputRange!(ElementType!RoR) && isInputRange!R && 
is(Unqual!(ElementType!(ElementType!RoR)) == 
Unqual!(ElementType!R)))
C:\D\dmd2\windows\bin\..\..\src\phobos\std\array.d(1573):        
std.array.join(RoR)(RoR ror) if (isInputRange!RoR && 
isInputRange!(ElementType!RoR))
[Finished in 0.3s]

"Dicebot" <public dicebot.lv> writes:

On Wednesday, 19 February 2014 at 13:07:39 UTC, Suliman wrote:
 Hm, I got next error on this code

 import std.stdio;
 import std.array;

 void main()
 {
 immutable s = ["red", "blue"];
 auto js = s.join;
 }

This works:

auto s = ["red", "blue"];
auto js = s.join("");

2 issues in your snippet:

1) need to define separator for join
2) fully immutable array can't act is InputRange as one can't 
popFront from it

Arguably join should have made constraint check on tail-qualified 
copy of s instead though (as it is legal to copy imutable(char[]) 
into immutable(char)[]). I bet there is even bugzilla entry for 
it :)

Timon Gehr <timon.gehr gmx.ch> writes:

On 02/19/2014 02:21 PM, Dicebot wrote:
 2 issues in your snippet:

 1) need to define separator for join

No, a custom separator is not mandatory.

"Dicebot" <public dicebot.lv> writes:

On Wednesday, 19 February 2014 at 13:52:06 UTC, Timon Gehr wrote:
 On 02/19/2014 02:21 PM, Dicebot wrote:
 2 issues in your snippet:

 1) need to define separator for join

 No, a custom separator is not mandatory.

Ah, my bad, was expecting a default parameter, not an extra
overload. See it now in docs.

"Gary Willoughby" <dev nomad.so> writes:

On Sunday, 16 February 2014 at 13:22:09 UTC, bearophile wrote:
 In the last days of beta3 D+Phobos is getting better in small 
 but significant ways:

 immutable s = ["red", "blue"];
 auto js = s.join;

 This is very handy because you can join arrays from constant 
 function arguments, or the result of a map that yields const 
 items, etc.

 -----------------------

 And I am finding the optional column number in error messages 
 very handy, my editor/IDE often jumps at the right column, 
 saving me tiny amounts of time that adds up making the 
 debugging nicer. The experience is just better than before.

 -----------------------

 auto r = [10, 20, 30].sum;

 This has replaced me tens of usages of:
 alias sum = reduce!q{a + b};
 Or:
 alias sum = curry!(reduce!q{a + b}, 0);


 But I have found problems because currently sum(int[]) returns 
 a long, see the discussion so far:
 https://d.puremagic.com/issues/show_bug.cgi?id=12169

 Bye,
 bearophile

What is q{a + b} ?

"Dicebot" <public dicebot.lv> writes:

On Wednesday, 19 February 2014 at 14:03:53 UTC, Gary Willoughby 
wrote:
 What is q{a + b} ?

http://dlang.org/lex.html#TokenString