2cded107cd
I'm changing the order of some more topics. Trying to explain the value of pointers when we're mostly dealing with stack-sized values like integers feels convoluted. So I'm starting with enums (which also has a nice segue from an earlier "switch" exercise). Then structs. Then unions (just in keeping with the order of these items on ziglearn.org) and THEN pointers and multi-pointers and slices.
50 lines
1.3 KiB
Zig
50 lines
1.3 KiB
Zig
//
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// Remember that little mathematical virtual machine we made using the
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// "unreachable" statement? Well, there were two problems with the
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// way we were using op codes:
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//
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// 1. Having to remember op codes by number is no good.
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// 2. We had to use "unreachable" because Zig had no way of knowing
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// how many valid op codes there were.
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//
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// An "enum" is a Zig construct that lets you give names to numeric
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// values and store them in a set. They look a lot like error sets:
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//
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// const Fruit = enum{ apple, pear, orange };
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//
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// const my_fruit = Fruit.apple;
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//
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// Let's use an enum in place of the numbers we were using in the
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// previous version!
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//
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const std = @import("std");
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// Please complete the enum!
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const Ops = enum{ ??? };
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pub fn main() void {
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const operations = [_]Ops{
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Ops.inc,
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Ops.inc,
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Ops.inc,
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Ops.pow,
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Ops.dec,
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Ops.dec
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};
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var current_value: u32 = 0;
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for (operations) |op| {
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switch (op) {
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Ops.inc => { current_value += 1; },
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Ops.dec => { current_value -= 1; },
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Ops.pow => { current_value *= current_value; },
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// No "else" needed! Why is that?
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}
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std.debug.print("{} ", .{current_value});
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}
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std.debug.print("\n", .{});
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}
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