diff options
Diffstat (limited to 'd.html.markdown')
-rw-r--r-- | d.html.markdown | 103 |
1 files changed, 57 insertions, 46 deletions
diff --git a/d.html.markdown b/d.html.markdown index daba8020..80c1dc65 100644 --- a/d.html.markdown +++ b/d.html.markdown @@ -1,6 +1,6 @@ --- -language: D -filename: learnd.d +language: D +filename: learnd.d contributors: - ["Nick Papanastasiou", "www.nickpapanastasiou.github.io"] lang: en @@ -18,13 +18,15 @@ void main(string[] args) { } ``` -If you're like me and spend way too much time on the internet, odds are you've heard +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 +multi-paradigm language with support for everything from low-level features to expressive high-level abstractions. -D is actively developed by Walter Bright and Andrei Alexandrescu, two super smart, really cool -dudes. With all that out of the way, let's look at some examples! +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! ```c import std.stdio; @@ -36,9 +38,10 @@ void main() { writeln(i); } - auto n = 1; // use auto for type inferred variables - - // Numeric literals can use _ as a digit seperator for clarity + // '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; } @@ -47,13 +50,15 @@ void main() { n -= (n / 2); } while(n > 0); - // For and while are nice, but in D-land we prefer foreach - // The .. creates a continuous range, excluding the end - foreach(i; 1..1_000_000) { + // 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(i; 1..1_000_000) { if(n % 2 == 0) writeln(i); } + // There's also 'foreach_reverse' when you want to loop backwards. foreach_reverse(i; 1..int.max) { if(n % 2 == 1) { writeln(i); @@ -69,16 +74,18 @@ are passed to functions by value (i.e. copied) and classes are passed by referen we can use templates to parameterize all of these on both types and values! ```c -// Here, T is a type parameter. Think <T> from C++/C#/Java +// Here, 'T' is a type parameter. Think '<T>' from C++/C#/Java. struct LinkedList(T) { T data = null; - LinkedList!(T)* next; // The ! is used to instaniate a parameterized type. Again, think <T> + + // 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 parens + + // If there is only one template parameter, we can omit the parentheses. BinTree!T left; BinTree!T right; } @@ -93,37 +100,34 @@ enum Day { Saturday, } -// Use alias to create abbreviations for types - +// 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) + if(a < b) return b; return a; } -// Use the ref keyword to ensure pass by referece. -// That is, even if a and b are value types, they -// will always be passed by reference to swap +// 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; + b = temp; } -// With templates, we can also parameterize on values, not just types +// 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 +auto mat = new Matrix!(3, 3); // We've defaulted type 'T' to 'int'. ``` @@ -133,25 +137,24 @@ have the syntax of POD structures (`structure.x = 7`) with the semantics of getter and setter methods (`object.setX(7)`)! ```c -// Consider a class parameterized on a types T, U - +// Consider a class parameterized on types 'T' & 'U'. class MyClass(T, U) { T _data; U _other; - } -// And "getter" and "setter" methods like so +// And "getter" and "setter" methods like so: class MyClass(T, U) { T _data; U _other; - - // Constructors are always named `this` + + // 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; @@ -161,7 +164,7 @@ class MyClass(T, U) { return _other; } - // setters + // setters @property void data(T t) { _data = t; } @@ -170,16 +173,24 @@ class MyClass(T, U) { _other = u; } } -// And we use them in this manner +// And we use them in this manner: void main() { - auto mc = MyClass!(int, string); + 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; - mc.data = 7; - mc.other = "seven"; - - writeln(mc.data); - writeln(mc.other); + // 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); } ``` @@ -193,7 +204,7 @@ and `override`ing 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` +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! @@ -205,7 +216,7 @@ 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 old function you like, but lambdas are convenient here. auto num = iota(1, 101).filter!(x => x % 2 == 0) @@ -216,12 +227,12 @@ void main() { } ``` -Notice how we got to build a nice Haskellian pipeline to compute 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. 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 +[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! |