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| author | Tapmemer <jeroen.w.van.der.veen@gmail.com> | 2018-02-20 09:36:50 +0100 | 
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| committer | GitHub <noreply@github.com> | 2018-02-20 09:36:50 +0100 | 
| commit | c1037971f83043bf30a73ba46cca0e8d3ade880e (patch) | |
| tree | 4f93e9132313019ee6d764f53f8724d694a7bb6e | |
| parent | acf13c548b2ada661b6fe9616fbf4926659a6590 (diff) | |
shouldnt copy 
shouldnt copy if i dont do anything with it
| -rw-r--r-- | nl-nl/d-nl.html.markdown | 260 | 
1 files changed, 0 insertions, 260 deletions
| diff --git a/nl-nl/d-nl.html.markdown b/nl-nl/d-nl.html.markdown deleted file mode 100644 index d2a57cae..00000000 --- a/nl-nl/d-nl.html.markdown +++ /dev/null @@ -1,260 +0,0 @@ ---- -language: D -filename: learnd.d -contributors: -    - ["Nick Papanastasiou", "www.nickpapanastasiou.github.io"] - ---- - -```d -// You know what's coming... -module hello; - -import std.stdio; - -// args is optional -void main(string[] args) { -    writeln("Hello, World!"); -} -``` - -If you're like me and spend way too much time on the internet, odds are you've heard -about [D](http://dlang.org/). The D programming language is a modern, general-purpose, -multi-paradigm language with support for everything from low-level features to -expressive high-level abstractions. - -D is actively developed by a large group of super-smart people and is spearheaded by -[Walter Bright](https://en.wikipedia.org/wiki/Walter_Bright) and -[Andrei Alexandrescu](https://en.wikipedia.org/wiki/Andrei_Alexandrescu). -With all that out of the way, let's look at some examples! - -```d -import std.stdio; - -void main() { - -    // Conditionals and loops work as expected. -    for(int i = 0; i < 10000; i++) { -        writeln(i); -    } - -    // 'auto' can be used for inferring types. -    auto n = 1; - -    // Numeric literals can use '_' as a digit separator for clarity. -    while(n < 10_000) { -        n += n; -    } - -    do { -        n -= (n / 2); -    } while(n > 0); - -    // For and while are nice, but in D-land we prefer 'foreach' loops. -    // The '..' creates a continuous range, including the first value -    // but excluding the last. -    foreach(n; 1..1_000_000) { -        if(n % 2 == 0) -            writeln(n); -    } - -    // There's also 'foreach_reverse' when you want to loop backwards. -    foreach_reverse(n; 1..int.max) { -        if(n % 2 == 1) { -            writeln(n); -        } else { -            writeln("No!"); -        } -    } -} -``` - -We can define new types with `struct`, `class`, `union`, and `enum`. Structs and unions -are passed to functions by value (i.e. copied) and classes are passed by reference. Furthermore, -we can use templates to parameterize all of these on both types and values! - -```d -// Here, 'T' is a type parameter. Think '<T>' from C++/C#/Java. -struct LinkedList(T) { -    T data = null; - -    // Use '!' to instantiate a parameterized type. Again, think '<T>'. -    LinkedList!(T)* next; -} - -class BinTree(T) { -    T data = null; - -    // If there is only one template parameter, we can omit the parentheses. -    BinTree!T left; -    BinTree!T right; -} - -enum Day { -    Sunday, -    Monday, -    Tuesday, -    Wednesday, -    Thursday, -    Friday, -    Saturday, -} - -// Use alias to create abbreviations for types. -alias IntList = LinkedList!int; -alias NumTree = BinTree!double; - -// We can create function templates as well! -T max(T)(T a, T b) { -    if(a < b) -        return b; - -    return a; -} - -// Use the ref keyword to ensure pass by reference. That is, even if 'a' and 'b' -// are value types, they will always be passed by reference to 'swap()'. -void swap(T)(ref T a, ref T b) { -    auto temp = a; - -    a = b; -    b = temp; -} - -// With templates, we can also parameterize on values, not just types. -class Matrix(uint m, uint n, T = int) { -    T[m] rows; -    T[n] columns; -} - -auto mat = new Matrix!(3, 3); // We've defaulted type 'T' to 'int'. - -``` - -Speaking of classes, let's talk about properties for a second. A property -is roughly a function that may act like an lvalue, so we can -have the syntax of POD structures (`structure.x = 7`) with the semantics of -getter and setter methods (`object.setX(7)`)! - -```d -// Consider a class parameterized on types 'T' & 'U'. -class MyClass(T, U) { -    T _data; -    U _other; -} - -// And "getter" and "setter" methods like so: -class MyClass(T, U) { -    T _data; -    U _other; - -    // Constructors are always named 'this'. -    this(T t, U u) { -        // This will call the setter methods below. -        data = t; -        other = u; -    } - -    // getters -    @property T data() { -        return _data; -    } - -    @property U other() { -        return _other; -    } - -    // setters -    @property void data(T t) { -        _data = t; -    } - -    @property void other(U u) { -        _other = u; -    } -} - -// And we use them in this manner: -void main() { -    auto mc = new MyClass!(int, string)(7, "seven"); - -    // Import the 'stdio' module from the standard library for writing to -    // console (imports can be local to a scope). -    import std.stdio; - -    // Call the getters to fetch the values. -    writefln("Earlier: data = %d, str = %s", mc.data, mc.other); - -    // Call the setters to assign new values. -    mc.data = 8; -    mc.other = "eight"; - -    // Call the getters again to fetch the new values. -    writefln("Later: data = %d, str = %s", mc.data, mc.other); -} -``` - -With properties, we can add any amount of logic to -our getter and setter methods, and keep the clean syntax of -accessing members directly! - -Other object-oriented goodies at our disposal -include interfaces, abstract classes, -and overriding methods. D does inheritance just like Java: -Extend one class, implement as many interfaces as you please. - -We've seen D's OOP facilities, but let's switch gears. D offers -functional programming with first-class functions, `pure` -functions, and immutable data. In addition, all of your favorite -functional algorithms (map, filter, reduce and friends) can be -found in the wonderful `std.algorithm` module! - -```d -import std.algorithm : map, filter, reduce; -import std.range : iota; // builds an end-exclusive range - -void main() { -    // We want to print the sum of a list of squares of even ints -    // from 1 to 100. Easy! - -    // Just pass lambda expressions as template parameters! -    // You can pass any function you like, but lambdas are convenient here. -    auto num = iota(1, 101).filter!(x => x % 2 == 0) -                           .map!(y => y ^^ 2) -                           .reduce!((a, b) => a + b); - -    writeln(num); -} -``` - -Notice how we got to build a nice Haskellian pipeline to compute num? -That's thanks to a D innovation know as Uniform Function Call Syntax (UFCS). -With UFCS, we can choose whether to write a function call as a method -or free function call! Walter wrote a nice article on this -[here.](http://www.drdobbs.com/cpp/uniform-function-call-syntax/232700394) -In short, you can call functions whose first parameter -is of some type A on any expression of type A as a method. - -I like parallelism. Anyone else like parallelism? Sure you do. Let's do some! - -```d -// Let's say we want to populate a large array with the square root of all -// consecutive integers starting from 1 (up until the size of the array), and we -// want to do this concurrently taking advantage of as many cores as we have -// available. - -import std.stdio; -import std.parallelism : parallel; -import std.math : sqrt; - -void main() { -    // Create your large array -    auto arr = new double[1_000_000]; - -    // Use an index, access every array element by reference (because we're -    // going to change each element) and just call parallel on the array! -    foreach(i, ref elem; parallel(arr)) { -        elem = sqrt(i + 1.0); -    } -} -``` | 
