diff --git a/hands-on_dlang.md b/hands-on_dlang.md index 074b4b7..b98156b 100644 --- a/hands-on_dlang.md +++ b/hands-on_dlang.md @@ -84,6 +84,7 @@ - [Example](#example) - [Executing unittests](#executing-unittests) - [Code coverage](#code-coverage) + - [String mixins](#string-mixins) ## Setup @@ -1240,7 +1241,6 @@ composed to express complex operations in a readable way. They are based on ranges and will work on your datatypes, if they implement the range interface. ```D -// Hey come on, just get the whole army! import std.algorithm : canFind, map, filter, sort, uniq, joiner, chunkBy, splitter; import std.array : array, empty; @@ -1248,12 +1248,11 @@ import std.range : zip; import std.stdio : writeln; import std.string : format; -void main() -{ - string text = q{This tour will give you an +void main() { + string text = `This tour will give you an overview of this powerful and expressive systems programming language which compiles directly -to efficient, *native* machine code.}; +to efficient, *native* machine code.`; // splitting predicate alias pred = c => canFind(" ,.\n", c); @@ -1297,8 +1296,7 @@ D has built-in unittests via a very simple syntax, which can appear anywhere in a D module: ```D -unittest -{ +unittest { assert(myAbs(-1) == 1); assert(myAbs(1) == 1); } @@ -1334,8 +1332,7 @@ struct Vector3 { } } -void main() -{ +void main() { Vector3 vec = Vector3(0,1,0); writeln(`This vector has been tested: `, vec); } @@ -1343,8 +1340,6 @@ void main() // Or just somewhere else unittest { Vector3 vec; - // .init a special built-in property that - // returns the initial value of type. assert(vec.x == double.init); } ``` @@ -1359,3 +1354,20 @@ using DUB, just run `dub test`. D also supports generating coverage reports out of the box, just compile with the `-cov` flag. When using DUB, just add the flag `--coverage`. + +### String mixins + +The mixin expression takes an arbitrary string and compiles it and generates instructions accordingly. This is a compile-time feature, so ths string needs +to be known at compile-time. + +```D +mixin("int b = 5"); // compiles just fine +assert(b == 5); + +static immutable compileTimeKnownString = q{int c = 5;}; +mixin(compileTimeKnownString); // so does this +assert(c == 5); + +immutable runTimeString = q{int c =5;}; +mixin(runTimeString); // compile error, runTimeString is not known at compile-time +```