http://techtalks.nsu.ru Видеозапись: http://www.youtube.com/watch?v=sfBrMhAxvFk 5 ноября 2013. DLang: возможности языка и его применение(Николай Толстокулаков, Ixtens) "Николай Толстокулаков (Ixtens) рассказывает об истории, синтаксисе и фичах языка D." Лекция прочитана в рамках проекта Tech Talks @NSU – серии открытых лекций о разработке ПО и карьере в IT, проводимых в Новосибирском государственном университете. Подробности: http://techtalks.nsu.ru

1. Dlang
Tolstokulakov Nikolay

2. Going to native
1. C++11
2. GoLang
3. Rust
4. DLang

3. Authors
Andrei Alexandrescu
● Modern C++ Design: Generic
Programming and Design Patterns
Applied
● C++ Coding Standards: 101 Rules,
Guidelines, and Best Practices.
● The D Programming Language.
Walter Bright
● C and C++ compilers:
○ Digital Mars C++
○ Symantec C++
○ Zortech C++ (the first native
C++ compiler)

4. Dlang.org
D is a language with C-like syntax and static typing. It
pragmatically combines efficiency, control, and modeling
power, with safety and programmer productivity.
● Convenience - minimal boilerplate, automatic memory management,
slices, ranges
● Power - polymorphism, value semantics, functional style, generics,
generative programming, contract programming, ... Innovative approach to
concurrency
● Efficiency - native code, native pointers, type casts, access to any C
function, and even inline assembly code

5. TIOBE Programming Community Index for
October 2013
21 R 0.553% 31 ABAP 0.394% 41 JavaFX Script 0.297%
22 SAS 0.543% 32 C shell 0.382% 42 Tcl 0.294%
23 Ada 0.510% 33 Common Lisp 0.380% 43 Erlang 0.292%
24 F# 0.499% 34 NXT-G 0.366% 44 Max/MSP 0.276%
25 Fortran 0.474% 35 Scheme 0.360% 45 Scratch 0.270%
26 Assembly 0.471% 36 Scala0.345% 46 Haskell 0.245%
27 Bash 0.470% 37 D 0.337% 47 ML 0.245%
28 Ladder Logic 0.457% 38 Prolog 0.328% 48 PL/I 0.240%
29 Logo 0.433% 39 RPG (OS/400) 0.319% 49 ActionScript 0.215%
30 Lua 0.413% 40 PostScript 0.312% 50 Emacs Lisp 0.210%

6. DLang
● It is complex (more 100 keywords vs 50 in Java)
● Syntactic sugar & features
○ slices, auto, powerful foreach, final switch, ...
○ unit tests, contract programming
○ compile time intersection
○ lamda, delegate
○ scope
○ ranges
○ anti-hijacking
○ ………
● Powerful metaprogramming

7. The sope statement (Java, C#)
(action)
try{
(next)
}catch(Exception e){
(rollback)
throw e
}finally{
(cleanup)
}

8. The scope statement
(actionN)
scope(failure) (rollbackN)
scope(exit) (cleanupN)
(actionN+1)
scope(failure) (rollbackN+1)
scope(exit) (cleanupN+1)

9. Built-in array
bool binarySearch(T)(T[] input, T value) {
if (input.empty) return false;
auto i = input.length / 2;
auto mid = input[i];
if (mid > value) return binarySearch(input[0 .. i]);
if (mid < value) return binarySearch(input[i + 1 .. $]);
return true;
}

10. Ranges
InputRange:
● front - get the first element of the range
● popFront - remove the first element of the range
● empty - are there more elements in the range?
InputRange
↑
ForwardRange
↗ ↖
BidirectionalRange RandomAccessRange (infinite)
↑
RandomAccessRange (finite)

11. Ranges - sort input stream #1
import std.array, std.algorithm, std.stdio;
void main(){
auto lines = stdin.byLine(KeepTerminator.yes);
auto dupLines = map!(a => a.idup)(lines);
auto arrLines = array(dupLines);
sort(arrLines);
copy(arrLines, stdout.lockingTextWriter());
}

12. Sort input stream #2 (UFCS)
#!/usr/bin/rdmd
import std.array, std.algorithm, std.stdio;
void main(){
stdin.byLine(KeepTerminator.yes)
.map!(a => a.idup)
.array
.sort
.copy(stdout.lockingTextWriter());
}

13. Voldemort типы
http://habrahabr.ru/post/183488/
auto generator(uint seed) {
struct RandomNumberGenerator {
@property int front() { return ((seed / 0x10000) * seed) >> 16; }
void popFront() { seed = seed * 1103515245 + 12345; }
@property bool empty() { return false; }
}
RandomNumberGenerator g;
g.popFront(); // get it going
return g;
}

14. Compile time functions - C++
template <int N> struct Factorial {
enum { value = N * Factorial<N - 1>::value };
};
template <> struct Factorial<0> {
enum { value = 1 };
};
void foo() {
int x = Factorial<0>::value; // == 1
int y = Factorial<4>::value; // == 24
}

15. Compile time - DLang
import std.stdio, std.bigint;
BigInt factorial(uint n){
BigInt rs = 1;
foreach(i; 1..n+1) rs *= i;
return rs;
}
enum f3 = factorial(20);
void main(){
writefln("%s - %s", f3, factorial(4));
}

16. Pegged
https://github.com/PhilippeSigaud/Pegged/
mixin(grammar(`
Arithmetic:
Term < Factor (Add / Sub)*
Add < "+" Factor
Sub < "-" Factor
Factor < Primary (Mul / Div)*
Mul < "*" Primary
Div < "/" Primary
……………..
`));

17. float interpreter(string expr){
auto p = Arithmetic(expr);
float value(ParseTree p) {
switch (p.name) {
case "Arithmetic":
return value(p.children[0]);
case "Arithmetic.Term":
………………………….
void main(string args[]){
pragma(msg, interpreter("1 + 2 - (3-5)*6"));
foreach(a; args[1 .. $]) writefln("%s = %s", a, interpreter(a));
}

18. Dynamic typing
http://wiki.dlang.org/Dynamic_typing
var fromArgs = var.fromJson(args[1]);
writefln("%s", fromArgs.keys);
uint ids[] = cast(uint[])fromArgs.keys;
var newIds = ids.map!(a=>a*2).array;
fromArgs.keys = newIds;
writefln("%s", fromArgs);
string strIds[] = cast(string[])fromArgs.keys;
var newStrIds = strIds.map!(a=>a~"!").array;
fromArgs.keys = newStrIds;
writefln("%s", fromArgs);
./jsvar_test '{"keys":[1,2,3]}'
[1, 2, 3]
{"keys":[2,4,6]}
{"keys":["2!","4!","6!"]}

19. Compilers, IDE, tools, …
http://wiki.dlang.org/The_D_Programming_Language
● Compilers: dmd, gdc, ldc
● IDE
○ DDT - Eclipse based
○ Mono-D
○ Visual-D

20. Materials
● dlang.org
● dconf.org
● The D Programming Language (Andrei
Alexandrescu)
● Three Unlikely Successful Features of D