diff options
Diffstat (limited to 'd.html.markdown')
-rw-r--r-- | d.html.markdown | 82 |
1 files changed, 45 insertions, 37 deletions
diff --git a/d.html.markdown b/d.html.markdown index 88a83e41..6f88cf84 100644 --- a/d.html.markdown +++ b/d.html.markdown @@ -53,15 +53,15 @@ void main() { // 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) { + foreach(n; 1..1_000_000) { if(n % 2 == 0) - writeln(i); + writeln(n); } // There's also 'foreach_reverse' when you want to loop backwards. - foreach_reverse(i; 1..int.max) { + foreach_reverse(n; 1..int.max) { if(n % 2 == 1) { - writeln(i); + writeln(n); } else { writeln("No!"); } @@ -70,20 +70,22 @@ void main() { ``` 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. Futhermore, +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! ```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 the parentheses + // If there is only one template parameter, we can omit the parentheses. BinTree!T left; BinTree!T right; } @@ -98,13 +100,11 @@ 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) return b; @@ -112,9 +112,8 @@ T max(T)(T a, T 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; @@ -122,13 +121,13 @@ void swap(T)(ref T a, ref T b) { 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'. ``` @@ -138,21 +137,20 @@ 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; } @@ -175,16 +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"); - mc.data = 7; - mc.other = "seven"; + // Import the 'stdio' module from the standard library for writing to + // console (imports can be local to a scope). + import std.stdio; - 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); } ``` @@ -193,8 +199,8 @@ our getter and setter methods, and keep the clean syntax of accessing members directly! Other object-oriented goodies at our disposal -include `interface`s, `abstract class`es, -and `override`ing methods. D does inheritance just like Java: +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 @@ -212,7 +218,7 @@ void main() { // 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. + // 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); @@ -222,7 +228,7 @@ void main() { ``` 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. +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) @@ -232,21 +238,23 @@ 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! ```c +// 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() { - // We want take the square root every number in our array, - // and take advantage of as many cores as we have available. + // Create your large array auto arr = new double[1_000_000]; - // Use an index, and an array element by referece, - // and just call parallel on the array! + // 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)) { ref = sqrt(i + 1.0); } } - - ``` |