mirror of
https://codeberg.org/ziglings/exercises.git
synced 2025-11-03 20:25:37 +00:00
109 lines
3.3 KiB
Zig
109 lines
3.3 KiB
Zig
//
|
|
// You can also put 'comptime' before a function parameter to
|
|
// enforce that the argument passed to the function must be known
|
|
// at compile time. We've actually been using a function like
|
|
// this the entire time, std.debug.print():
|
|
//
|
|
// fn print(comptime fmt: []const u8, args: anytype) void
|
|
//
|
|
// Notice that the format string parameter 'fmt' is marked as
|
|
// 'comptime'. One of the neat benefits of this is that the
|
|
// format string can be checked for errors at compile time rather
|
|
// than crashing at runtime.
|
|
//
|
|
// (The actual formatting is done by std.fmt.format() and it
|
|
// contains a complete format string parser that runs entirely at
|
|
// compile time!)
|
|
//
|
|
const print = @import("std").debug.print;
|
|
|
|
// This struct is the model of a model boat. We can transform it
|
|
// to any scale we would like: 1:2 is half-size, 1:32 is
|
|
// thirty-two times smaller than the real thing, and so forth.
|
|
const Schooner = struct {
|
|
name: []const u8,
|
|
scale: u32 = 1,
|
|
hull_length: u32 = 143,
|
|
bowsprit_length: u32 = 34,
|
|
mainmast_height: u32 = 95,
|
|
|
|
fn scaleMe(self: *Schooner, comptime scale: u32) void {
|
|
var my_scale = scale;
|
|
|
|
// We did something neat here: we've anticipated the
|
|
// possibility of accidentally attempting to create a
|
|
// scale of 1:0. Rather than having this result in a
|
|
// divide-by-zero error at runtime, we've turned this
|
|
// into a compile error.
|
|
//
|
|
// This is probably the correct solution most of the
|
|
// time. But our model boat model program is very casual
|
|
// and we just want it to "do what I mean" and keep
|
|
// working.
|
|
//
|
|
// Please change this so that it sets a 0 scale to 1
|
|
// instead.
|
|
if (my_scale == 0) @compileError("Scale 1:0 is not valid!");
|
|
|
|
self.scale = my_scale;
|
|
self.hull_length /= my_scale;
|
|
self.bowsprit_length /= my_scale;
|
|
self.mainmast_height /= my_scale;
|
|
}
|
|
|
|
fn printMe(self: Schooner) void {
|
|
print("{s} (1:{}, {} x {})\n", .{
|
|
self.name,
|
|
self.scale,
|
|
self.hull_length,
|
|
self.mainmast_height,
|
|
});
|
|
}
|
|
};
|
|
|
|
pub fn main() void {
|
|
var whale = Schooner{ .name = "Whale" };
|
|
var shark = Schooner{ .name = "Shark" };
|
|
var minnow = Schooner{ .name = "Minnow" };
|
|
|
|
// Hey, we can't just pass this runtime variable as an
|
|
// argument to the scaleMe() method. What would let us do
|
|
// that?
|
|
var scale: u32 = undefined;
|
|
|
|
scale = 32; // 1:32 scale
|
|
|
|
minnow.scaleMe(scale);
|
|
minnow.printMe();
|
|
|
|
scale -= 16; // 1:16 scale
|
|
|
|
shark.scaleMe(scale);
|
|
shark.printMe();
|
|
|
|
scale -= 16; // 1:0 scale (oops, but DON'T FIX THIS!)
|
|
|
|
whale.scaleMe(scale);
|
|
whale.printMe();
|
|
}
|
|
//
|
|
// Going deeper:
|
|
//
|
|
// What would happen if you DID attempt to build a model in the
|
|
// scale of 1:0?
|
|
//
|
|
// A) You're already done!
|
|
// B) You would suffer a mental divide-by-zero error.
|
|
// C) You would construct a singularity and destroy the
|
|
// planet.
|
|
//
|
|
// And how about a model in the scale of 0:1?
|
|
//
|
|
// A) You're already done!
|
|
// B) You'd arrange nothing carefully into the form of the
|
|
// original nothing but infinitely larger.
|
|
// C) You would construct a singularity and destroy the
|
|
// planet.
|
|
//
|
|
// Answers can be found on the back of the Ziglings packaging.
|