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78 lines
2.5 KiB
Zig
78 lines
2.5 KiB
Zig
//
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// Now that we've seen how methods work, let's see if we can help
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// our elephants out a bit more with some Elephant methods.
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//
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const std = @import("std");
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const Elephant = struct {
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letter: u8,
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tail: ?*Elephant = null,
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visited: bool = false,
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// New Elephant methods!
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pub fn getTail(self: *Elephant) *Elephant {
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return self.tail.?; // Remember, this means "orelse unreachable"
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}
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pub fn hasTail(self: *Elephant) bool {
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return (self.tail != null);
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}
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pub fn visit(self: *Elephant) void {
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self.visited = true;
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}
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pub fn print(self: *Elephant) void {
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// Prints elephant letter and [v]isited
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const v: u8 = if (self.visited) 'v' else ' ';
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std.debug.print("{u}{u} ", .{ self.letter, v });
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}
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};
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pub fn main() void {
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var elephantA = Elephant{ .letter = 'A' };
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var elephantB = Elephant{ .letter = 'B' };
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var elephantC = Elephant{ .letter = 'C' };
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// This links the elephants so that each tail "points" to the next.
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elephantA.tail = &elephantB;
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elephantB.tail = &elephantC;
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visitElephants(&elephantA);
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std.debug.print("\n", .{});
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}
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// This function visits all elephants once, starting with the
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// first elephant and following the tails to the next elephant.
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fn visitElephants(first_elephant: *Elephant) void {
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var e = first_elephant;
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while (true) {
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e.print();
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e.visit();
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// This gets the next elephant or stops:
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// which method do we want here?
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e = if (e.hasTail()) e.getTail() else break;
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}
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}
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// Zig's enums can also have methods! This comment originally asked
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// if anyone could find instances of enum methods in the wild. The
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// first five pull requests were accepted and here they are:
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//
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// 1) drforester - I found one in the Zig source:
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// https://github.com/ziglang/zig/blob/041212a41cfaf029dc3eb9740467b721c76f406c/src/Compilation.zig#L2495
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//
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// 2) bbuccianti - I found one!
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// https://github.com/ziglang/zig/blob/6787f163eb6db2b8b89c2ea6cb51d63606487e12/lib/std/debug.zig#L477
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//
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// 3) GoldsteinE - Found many, here's one
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// https://github.com/ziglang/zig/blob/ce14bc7176f9e441064ffdde2d85e35fd78977f2/lib/std/target.zig#L65
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//
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// 4) SpencerCDixon - Love this language so far :-)
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// https://github.com/ziglang/zig/blob/a502c160cd51ce3de80b3be945245b7a91967a85/src/zir.zig#L530
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//
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// 5) tomkun - here's another enum method
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// https://github.com/ziglang/zig/blob/4ca1f4ec2e3ae1a08295bc6ed03c235cb7700ab9/src/codegen/aarch64.zig#L24
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