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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 /nl-nl | |
parent | acf13c548b2ada661b6fe9616fbf4926659a6590 (diff) |
shouldnt copy
shouldnt copy if i dont do anything with it
Diffstat (limited to 'nl-nl')
-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); - } -} -``` |