diff options
| -rw-r--r-- | exercises/047_methods.zig | 43 |
1 files changed, 24 insertions, 19 deletions
diff --git a/exercises/047_methods.zig b/exercises/047_methods.zig index 96d4c8e..7211caa 100644 --- a/exercises/047_methods.zig +++ b/exercises/047_methods.zig @@ -2,9 +2,9 @@ // Help! Evil alien creatures have hidden eggs all over the Earth // and they're starting to hatch! // -// Before you jump into battle, you'll need to know four things: +// Before you jump into battle, you'll need to know three things: // -// 1. You can attach functions to structs: +// 1. You can attach functions to structs (and other "type definitions"): // // const Foo = struct{ // pub fn hello() void { @@ -12,31 +12,34 @@ // } // }; // -// 2. A function that is a member of a struct is a "method" and is -// called with the "dot syntax" like so: +// 2. A function that is a member of a struct is "namespaced" within +// that struct and is called by specifying the "namespace" and then +// using the "dot syntax": // // Foo.hello(); // -// 3. The NEAT feature of methods is the special parameter named -// "self" that takes an instance of that type of struct: +// 3. The NEAT feature of these functions is that if they take either +// an instance of the struct or a pointer to an instance of the struct +// then they have some syntax sugar: // // const Bar = struct{ -// number: u32, -// -// pub fn printMe(self: Bar) void { -// std.debug.print("{}\n", .{self.number}); -// } +// pub fn a(self: Bar) void { _ = self; } +// pub fn b(this: *Bar, other: u8) void { _ = this; _ = other; } +// pub fn c(bar: *const Bar) void { _ = bar; } // }; // -// (Actually, you can name the first parameter anything, but -// please follow convention and use "self".) +// var bar = Bar{}; +// bar.a() // is equivalent to Bar.a(bar) +// bar.b(3) // is equivalent to Bar.b(&bar, 3) +// bar.c() // is equivalent to Bar.c(&bar) // -// 4. Now when you call the method on an INSTANCE of that struct -// with the "dot syntax", the instance will be automatically -// passed as the "self" parameter: +// Notice that the name of the parameter doesn't matter. Some use +// self, others use a lowercase version of the type name, but feel +// free to use whatever is most appropriate. // -// var my_bar = Bar{ .number = 2000 }; -// my_bar.printMe(); // prints "2000" +// Effectively, the method syntax sugar just does this transformation: +// thing.function(args); +// @TypeOf(thing).function(thing, args); // // Okay, you're armed. // @@ -63,7 +66,9 @@ const HeatRay = struct { // We love this method: pub fn zap(self: HeatRay, alien: *Alien) void { - alien.health -= if (self.damage >= alien.health) alien.health else self.damage; + alien.health -|= self.damage; // Saturating inplace substraction + // It subtracts but doesn't go below the + // lowest value for our type (in this case 0) } }; |