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//
// 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:
//
// 1. You can attach functions to structs:
//
// const Foo = struct{
// pub fn hello() void {
// std.debug.print("Foo says hello!\n", .{});
// }
// }
//
// 2. A function that is a member of a struct is a "method" and is
// called with the "dot syntax" like so:
//
// Foo.hello();
//
// 3. The NEAT feature of methods is the special parameter named
// "self" that takes an instance of that type of struct:
//
// const Bar = struct{
// number: u32,
//
// pub fn printMe(self: *Bar) void {
// std.debug.print("{}\n", .{self.number});
// }
// }
//
// (Actually, you can name the first parameter anything, but
// please follow convention and use "self".)
//
// 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:
//
// var my_bar = Bar{ .number = 2000 };
// my_bar.printMe(); // prints "2000"
//
// Okay, you're armed.
//
// Now, please zap the alien structs until they're all gone or
// Earth will be doomed!
//
const std = @import("std");
// Look at this hideous Alien struct. Know your enemy!
const Alien = struct {
health: u8,
// We hate this method:
pub fn hatch(strength: u8) Alien {
return Alien{
.health = strength * 5,
};
}
// We love this method:
pub fn zap(self: *Alien, damage: u8) void {
self.health -= if (damage >= self.health) self.health else damage;
}
};
pub fn main() void {
// Look at all of these aliens of various strengths!
var aliens = [_]Alien{
Alien.hatch(2),
Alien.hatch(1),
Alien.hatch(3),
Alien.hatch(3),
Alien.hatch(5),
Alien.hatch(3),
};
var aliens_alive = aliens.len;
var heat_ray_strength: u8 = 7; // We've been given a heat ray weapon.
// We'll keep checking to see if we've killed all the aliens yet.
while (aliens_alive > 0) {
aliens_alive = 0;
// Loop through every alien by reference (* makes a pointer capture value)
for (aliens) |*alien| {
// *** Zap the Alien Here! ***
???.zap(heat_ray_strength);
// If the alien's health is still above 0, it's still alive.
if (alien.health > 0) aliens_alive += 1;
}
std.debug.print("{} aliens. ", .{aliens_alive});
}
std.debug.print("Earth is saved!\n", .{});
}
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