66 lines
1.7 KiB
Zig
66 lines
1.7 KiB
Zig
//
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// As a matter of fact, you can put 'comptime' in front of any
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// expression to force it to be run at compile time.
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//
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// Execute a function:
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//
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// comptime llama();
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//
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// Get a value:
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//
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// bar = comptime baz();
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//
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// Execute a whole block:
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//
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// comptime {
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// bar = baz + biff();
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// llama(bar);
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// }
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//
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// Get a value from a block:
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//
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// var llama = comptime bar: {
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// const baz = biff() + bonk();
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// break :bar baz;
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// }
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//
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const print = @import("std").debug.print;
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const llama_count = 5;
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const llamas = [llama_count]u32{ 5, 10, 15, 20, 25 };
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pub fn main() void {
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// We meant to fetch the last llama. Please fix this simple
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// mistake so the assertion no longer fails.
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const my_llama = getLlama(4);
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print("My llama value is {}.\n", .{my_llama});
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}
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fn getLlama(comptime i: usize) u32 {
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// We've put a guard assert() at the top of this function to
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// prevent mistakes. The 'comptime' keyword here means that
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// the mistake will be caught when we compile!
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//
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// Without 'comptime', this would still work, but the
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// assertion would fail at runtime with a PANIC, and that's
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// not as nice.
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//
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// Unfortunately, we're going to get an error right now
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// because the 'i' parameter needs to be guaranteed to be
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// known at compile time. What can you do with the 'i'
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// parameter above to make this so?
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comptime assert(i < llama_count);
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return llamas[i];
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}
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// Fun fact: this assert() function is identical to
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// std.debug.assert() from the Zig Standard Library.
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fn assert(ok: bool) void {
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if (!ok) unreachable;
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}
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//
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// Bonus fun fact: I accidentally replaced all instances of 'foo'
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// with 'llama' in this exercise and I have no regrets!
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